Antibiotic resistance is a form of drug resistance whereby some (or, less commonly, all) sub-populations of a microorganism, usually a bacterial species, are able to survive after exposure to one or more antibiotics; pathogens resistant to multiple antibiotics are considered multidrug resistant (MDR) or, more colloquially, superbugs.
Antibiotic resistance is a serious and growing phenomenon in contemporary medicine and has emerged as one of the pre-eminent public health concerns of the 21st century, in particular as it pertains to pathogenic organisms (the term is especially relevant to organisms that cause disease in humans). A World Health Organization report released April 30, 2014 states, "this serious threat is no longer a prediction for the future, it is happening right now in every region of the world and has the potential to affect anyone, of any age, in any country. Antibiotic resistance–when bacteria change so antibiotics no longer work in people who need them to treat infections–is now a major threat to public health."
In the simplest cases, drug-resistant organisms may have acquired resistance to first-line antibiotics, thereby necessitating the use of second-line agents. Typically, a first-line agent is selected on the basis of several factors including safety, availability, and cost; a second-line agent is usually broader in spectrum, has a less favourable risk-benefit profile, and is more expensive or, in dire circumstances, may be locally unavailable. In the case of some MDR pathogens, resistance to second- and even third-line antibiotics is, thus, sequentially acquired, a case quintessentially illustrated by Staphylococcus aureus in some nosocomial settings. Some pathogens, such as Pseudomonas aeruginosa, also possess a high level of intrinsic resistance.
It may take the form of a spontaneous or induced genetic mutation, or the acquisition of resistance genes from other bacterial species by horizontal gene transfer via conjugation, transduction, or transformation. Many antibiotic resistance genes reside on transmissible plasmids, facilitating their transfer. Exposure to an antibiotic naturally selects for the survival of the organisms with the genes for resistance. In this way, a gene for antibiotic resistance may readily spread through an ecosystem of bacteria. Antibiotic-resistance plasmids frequently contain genes conferring resistance to several different antibiotics. This is not the case for Mycobacterium tuberculosis, the bacteria that causes Tuberculosis, since evidence is lacking for whether these bacteria have plasmids. Also M. tuberculosis lack the opportunity to interact with other bacteria in order to share plasmids.
Genes for resistance to antibiotics, like the antibiotics themselves, are ancient. However, the increasing prevalence of antibiotic-resistant bacterial infections seen in clinical practice stems from antibiotic use both within human medicine and veterinary medicine. Any use of antibiotics can increase selective pressure in a population of bacteria to allow the resistant bacteria to thrive and the susceptible bacteria to die off. As resistance towards antibiotics becomes more common, a greater need for alternative treatments arises. However, despite a push for new antibiotic therapies, there has been a continued decline in the number of newly approved drugs. Antibiotic resistance therefore poses a significant problem.
The growing prevalence and incidence of infections due to MDR pathogens is epitomised by the increasing number of familiar acronyms used to describe the causative agent and sometimes the infection; of these, MRSA is probably the most well-known, but others including VISA (vancomycin-intermediate S. aureus), VRSA (vancomycin-resistant S. aureus), ESBL (Extended spectrum beta-lactamase), VRE (Vancomycin-resistant Enterococcus) and MRAB (Multidrug-resistant A. baumannii) are prominent examples. Nosocomial infections overwhelmingly dominate cases where MDR pathogens are implicated, but multidrug-resistant infections are also becoming increasingly common in the community.
- 1 Cause
- 2 Environmental impact
- 3 Mechanisms
- 4 Resistant pathogens
- 5 Prevention
- 6 Research
- 7 See also
- 8 Footnotes
- 9 References
- 10 External links
Although there were low levels of preexisting antibiotic-resistant bacteria before the widespread use of antibiotics,  evolutionary pressure from their use has played a role in the development of multidrug-resistant varieties and the spread of resistance between bacterial species. The widespread use of antibiotics both inside and outside medicine is playing a significant role in the emergence of resistant bacteria.
In some countries, antibiotics are sold over the counter without a prescription, which also leads to the creation of resistant strains. Other practices contributing to resistance include antibiotic use in livestock feed to promote faster growth. Household use of antibacterials in soaps and other products, although not clearly contributing to resistance, is also discouraged (as not being effective at infection control). Unsound practices in the pharmaceutical manufacturing industry can also contribute towards the likelihood of creating antibiotic-resistant strains. The procedures and clinical practice during the period of drug treatment are frequently flawed — usually no steps are taken to isolate the patient to prevent re-infection or infection by a new pathogen, negating the goal of complete destruction by the end of the course (see Healthcare-associated infections and Infection control).
Certain antibiotic classes are more highly associated with colonisation with "superbugs" compared to other antibiotic classes. A superbug, also called multiresistant, is a bacterium that carries several resistance genes. The risk for colonisation increases if there is a lack of susceptibility (resistance) of the superbugs to the antibiotic used and high tissue penetration, as well as broad-spectrum activity against "good bacteria". In the case of MRSA, increased rates of MRSA infections are seen with glycopeptides, cephalosporins, and especially quinolones. In the case of colonisation with Clostridium difficile, the high-risk antibiotics include cephalosporins and in particular quinolones and clindamycin.
There is evidence that naturally occurring antibiotic resistance is common. The genes that confer this resistance are known as the environmental resistome. These genes may be transferred from non-disease-causing bacteria to those that do cause disease, leading to clinically significant antibiotic resistance.
In 1952, an experiment conducted by Joshua and Esther Lederberg showed that penicillin-resistant bacteria existed before penicillin treatment. While experimenting at the University of Wisconsin-Madison, Joshua Lederberg and his graduate student Norton Zinder also demonstrated preexistent bacterial resistance to streptomycin. In 1962, the presence of penicillinase was detected in dormant Bacillus licheniformis endospores, revived from dried soil on the roots of plants, preserved since 1689 in the British Museum. Six strains of Clostridium, found in the bowels of William Braine and John Hartnell (members of the Franklin Expedition) showed resistance to cefoxitin and clindamycin. It was suggested that penicillinase may have emerged as a defense mechanism for bacteria in their habitats, such as the case of penicillinase-rich Staphylococcus aureus, living with penicillin-producing Trichophyton, however this was deemed circumstantial. Search for a penicillinase ancestor has focused on the class of proteins that must be a priori capable of specific combination with penicillin. The resistance to cefoxitin and clindamycin in turn was attributed to Braine's and Hartnell's contact with microorganisms that naturally produce them or random mutation in the chromosomes of Clostridium strains. Nonetheless there is evidence that heavy metals and some pollutants may select for antibiotic-resistant bacteria, generating a constant source of them in small numbers.
The volume of antibiotic prescribed is the major factor in increasing rates or bacterial resistance rather than compliance with antibiotics. Inappropriate prescribing of antibiotics has been attributed to a number of causes, including people insisting on antibiotics, physicians prescribing them as they feel they do not have time to explain why they are not necessary, and physicians not knowing when to prescribe antibiotics or being overly cautious for medical and/or legal reasons. For example, a third of people believe that antibiotics are effective for the common cold, and the common cold is the most common reason antibiotics are prescribed even though antibiotics are useless against viruses. A single regimen of antibiotics even in compliant patients leads to a greater risk of resistant organisms to that antibiotic in the person for a month to possibly a year.
Antibiotic resistance has been shown to increase with duration of treatment; therefore, as long as a effective lower limit is observed, the use by the medical community of shorter courses of antibiotics is likely to decrease rates of resistance, reduce cost, and have better outcomes due to fewer complications such as C. difficile infection and diarrhea. In some situations a short course is inferior to a long course.
A BMJ editorial recommended that antibiotics can often be safely stopped 72 hours after symptoms resolve. Because patients may feel better before the infection is eradicated, doctors must provide instructions to patients so they know when it is safe to stop taking a prescription. Some researchers advocate doctors' using a very short course of antibiotics, reevaluating the patient after a few days, and stopping treatment if there are no longer clinical signs of infection.
Patients taking less than the required dosage or failing to take their doses within the prescribed timing results in decreased concentration of antibiotics in the bloodstream and tissues, and, in turn, exposure of bacteria to suboptimal antibiotic concentrations increases the frequency of antibiotic resistant organisms, however factors within the intensive care unit setting such as mechanical ventilation and multiple underlying diseases also appeared to contribute to bacterial resistance. These nosocomial pneumonia patients represented a situation where there was relatively little contribution of host defense to outcome, and therefore may not be applicable to otherwise healthy individuals taking antibiotics.
The improper use of antibiotics and therapeutic treatments can often be attributed to the presence of structural violence in particular regions. Socioeconomic factors such as race and poverty affect the accessibility of and adherence to drug therapy. The efficacy of treatment programs for these drug-resistant strains depends on whether or not programmatic improvements take into account the effects of structural violence.
The emergence of antibiotic-resistant microorganisms in human medicine is primarily the result of the use of antibiotics in humans, although the use of antibiotics in animals is also partly responsible.
Since the last third of the 20th century, there has been extensive use of antibiotics in animal husbandry. Some of these drugs are not considered significant for use in humans, because of their lack of either efficacy or purpose in humans (such as the use of ionopores in ruminants), or because that drug has mostly gone out of use in humans (such as sulfa drugs due to widespread allergic reactions and antibiotic resistance among human pathogens). Others however are used in both animals and humans, including penicillin and some forms of tetracycline. Historically, regulation of antibiotic use in food animals has been limited to limiting drug residues in meat, egg, and milk products, rather than by direct concern over the development of antibiotic resistance. This mirrors the primary concerns in human medicine, where, in general, researchers and doctors were more concerned about effective but non-toxic doses of drugs rather than antibiotic resistance.
The resistant bacteria which antibiotic exposure selects in animals can be transmitted to humans via three pathways, those being through the consumption of animal products (milk, meat, eggs, etc.), from close or direct contact with animals or other humans, or through the environment. In the first pathway, food preservation methods can help eliminate, decrease, or prevent the growth of bacteria in some food classes. Evidence for the transfer of antibiotic- resistant microorganisms from animals to humans has been scant, and most evidence shows that pathogens of concern in human populations originated in humans and are maintained there, with rare cases of transference to humans. The use of antibiotics in animals can be classified into different use patterns according to its purpose. The most accepted classification discriminates therapeutic, prophylactic, metaphylactic, and growth promotion uses of antibiotics. All four patterns select for bacterial resistance, since antibiotic resistance is a natural evolutionary process, but the non-therapeutic uses expose larger number of animals, and therefore of bacteria, for more extended periods, and at lower doses. They therefore greatly increase the cross-section for the evolution of resistance.
The World Health Organization concluded that inappropriate use of antibiotics in animal husbandry is an underlying contributor to the emergence and spread of antibiotic-resistant germs, and that the use of antibiotics as growth promoters in animal feeds should be prohibited, in the absence of risk assessments. Regarding this matter, the OIE has added to the Terrestrial Animal Health Code a series of guidelines with recommendations to its members for the creation and harmonization of national antimicrobial resistance surveillance and monitoring programs, monitoring of the quantities of antibiotics used in animal husbandry, and recommendations to ensure the proper and prudent use of antibiotic substances. Another guideline introduced in the terrestrial Animal Health Code is the implementation of methodologies that help to establish risk factors associated with this worldwide concern. The OIE concluded that risk assessments should be performed in order to assess, manage and define the possible health risks of antibiotic resistance in human and animal populations.
In the world, antibiotics are widely used on animals. As in human medicine, antibiotics can often be bought without prescription and veterinary supervision for use on pets and livestock. Bacteria remaining in these animals are likely to be resistant to the antibiotics used, and may be passed into the environment by the excretion and secretion of materials such as milk, feces, urine, saliva, semen, lochia, etc. The actual impact of these resistant germs depends on their specific type and on the animal or organism they henceforth infect. Some germs, such as tetanus, are toxic regardless of their antibiotic-resistant status. (It is useful to remember that antibiotics are not used in treatment of all diseases caused by bacteria. Tetanus, as an example, is prevented by vaccine and is extremely difficult to treat once symptoms appear.)
In 1998, European Union health ministers voted to ban four antibiotics widely used to promote animal growth (despite their scientific panel's recommendations). Regulation banning the use of antibiotics in European feed, with the exception of two antibiotics in poultry feeds, became effective in 2006. In Scandinavia, there is evidence that the ban has led to a lower prevalence of antimicrobial resistance in (nonhazardous) animal bacterial populations. However, a corresponding change in antibiotic-resistance cases among humans has not yet been demonstrated.
In the United States, the United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) collect data on antibiotic use in animals and humans. In research studies, occasional animal-to-human spread of drug-resistant organisms has been demonstrated. Antibiotics and other drugs are used in U.S. animal feed to promote animal productivity. In particular, poultry feed and water is a common route of administration of drugs, due to higher overall costs when drugs are administered by handling animals individually. In general, animals that appear ill are not permitted to be slaughtered for human consumption in the United States.
Growing U.S. consumer concern about using antibiotics in animal feed has led to a niche market of "antibiotic-free" animal products, but this small market is unlikely to change entrenched, industry-wide practices.
In 2001, the Union of Concerned Scientists estimated that greater than 70% of the antibiotics used in the U.S. are given to food animals (for example, chickens, pigs, and cattle), in the absence of disease. The amounts given are termed "sub-therapeutic", i.e., insufficient to combat disease. Despite no diagnosis of disease, the administration of these drugs (most of which are not significant to human medicine) results in decreased mortality and morbidity and increased growth in the animals so treated. It is theorized that sub-therapeutic dosages kills some, but not all, of the bacterial organisms in the animal — likely leaving those that are naturally antibiotic-resistant. Studies have shown, however, that, in essence, the overall population levels of bacteria are unchanged; only the mix of bacteria is affected.
The actual mechanism by which sub-therapeutic antibiotic feed additives serve as growth promoters is thus unclear. Some people have speculated that animals and fowl may have sub-clinical infections, which would be cured by low levels of antibiotics in feed, thereby allowing the creatures to thrive. No convincing evidence has been advanced for this theory, and the bacterial load in an animal is essentially unchanged by use of antibiotic feed additives. The mechanism of growth promotion is therefore probably something other than "killing off the bad bugs."
In 2000, the FDA announced their intention to revoke approval of fluoroquinolone use in poultry production because of substantial evidence linking it to the emergence of fluoroquinolone-resistant Campylobacter infections in humans. Legal challenges from the food animal and pharmaceutical industries delayed the final decision to do so until 2006. Fluroquinolones have been banned from extra-label use in food animals in the USA since 2007. However, they remain widely used in companion and exotic animals.
In 2001, National Hog Farmer magazine warned U.S. producers that C. difficile "is sweeping the industry, killing many piglets" (Neutkens D; "New Clostridium Claiming Baby Pigs"). In 2006, a study by the USDA's National Animal Health Monitoring System further investigated the prevalence of C. difficile in hog farms. The study, which covered hog farms of a size typical of those producing 94% of US swine, found the prevalence of C. difficile "relatively low (11.4%)" and that there was no difference in region or in size of farm. Human infection with C. difficile (either drug-resistant or not) is most commonly associated with the use of strong antibiotics in hospitalized humans, and is not associated with humans in contact with farm animals.
During 2007, two federal bills (S. 549 and H.R. 962) aimed at phasing out "nontherapeutic" antibiotics in U.S. food animal production. The Senate bill, introduced by Sen. Edward "Ted" Kennedy, died. The House bill, introduced by Rep. Louise Slaughter, died after being referred to Committee.
In the United States, the FDA first determined in 1977 that there is evidence of emergence of antibiotic-resistant bacterial strains in livestock. The long-established practice of permitting OTC sales of antibiotics (including penicillin and other drugs) to lay animal owners for administration to their own animals nonetheless continued in all states. In March 2012, the United States District Court for the Southern District of New York, ruling in an action brought by the Natural Resources Defense Council and others, ordered the FDA to revoke approvals for the use of antibiotics in livestock that violated FDA regulations. On April 11, 2012 the FDA announced a voluntary program to phase out unsupervised use of drugs as feed additives and convert approved over-the-counter uses for antibiotics to prescription use only, requiring veterinarian supervision of their use and a prescription. In December 2013, the FDA announced the commencement of these steps to phase out the use of antibiotics for the purposes of promoting livestock growth.
Antibiotics have been polluting the environment since their introduction through human waste (medication, farming), animals, and the pharmaceutical industry. Along with antibiotic waste, resistant bacteria follow, thus introducing antibiotic-resistant bacteria into the environment. As bacteria replicate quickly, the resistant bacteria that enter the environment replicate their resistance genes as they continue to divide. In addition, bacteria carrying resistance genes have the ability to spread those genes to other species via horizontal gene transfer. Therefore, even if the specific antibiotic is no longer introduced into the environment, antibiotic-resistance genes will persist through the bacteria that have since replicated without continuous exposure.
A study the Poudre River (Colorado, United States) implicated wastewater treatment plants, as well as animal-feeding operations in the dispersal of antibiotic-resistance genes into the environment. This research was done using molecular signatures in order to determine the sources, and the location at the Poudre River was chosen due to lack of other anthropogenic influences upstream. The study indicates that monitoring of antibiotic-resistance genes may be useful in determining not only the point of origin of their release but also how these genes persist in the environment. In addition, studying physical and chemical methods of treatment may alleviate pressure of antibiotic-resistance genes in the environment, and thus their entry back into human contact.
Antibiotic resistance can be a result of horizontal gene transfer, and also of unlinked point mutations in the pathogen genome at a rate of about 1 in 108 per chromosomal replication. The antibiotic action against the pathogen can be seen as an environmental pressure. Those bacteria with a mutation that allows them to survive live to reproduce. They then pass this trait to their offspring, which leads to the evolution of a fully resistant colony.
The four main mechanisms by which microorganisms exhibit resistance to antimicrobials are:
- Drug inactivation or modification: for example, enzymatic deactivation of penicillin G in some penicillin-resistant bacteria through the production of β-lactamases.
- Alteration of target site: for example, alteration of PBP—the binding target site of penicillins—in MRSA and other penicillin-resistant bacteria
- Alteration of metabolic pathway: for example, some sulfonamide-resistant bacteria do not require para-aminobenzoic acid (PABA), an important precursor for the synthesis of folic acid and nucleic acids in bacteria inhibited by sulfonamides, instead, like mammalian cells, they turn to using preformed folic acid.
- Reduced drug accumulation: by decreasing drug permeability or increasing active efflux (pumping out) of the drugs across the cell surface
There are three known mechanisms of fluoroquinolone resistance. Some types of efflux pumps can act to decrease intracellular quinolone concentration. In Gram-negative bacteria, plasmid-mediated resistance genes produce proteins that can bind to DNA gyrase, protecting it from the action of quinolones. Finally, mutations at key sites in DNA gyrase or topoisomerase IV can decrease their binding affinity to quinolones, decreasing the drug's effectiveness. Research has shown the bacterial protein LexA may play a key role in the acquisition of bacterial mutations giving resistance to quinolones and rifampicin.
Antibiotic resistance can also be introduced artificially into a microorganism through laboratory protocols, sometimes used as a selectable marker to examine the mechanisms of gene transfer or to identify individuals that absorbed a piece of DNA that included the resistance gene and another gene of interest. A recent study demonstrated that the extent of horizontal gene transfer among Staphylococcus is much greater than previously expected—and encompasses genes with functions beyond antibiotic resistance and virulence, and beyond genes residing within the mobile genetic elements.
For a long time, it has been thought that, for a microorganism to become resistant to an antibiotic, it must be in a large population. However, recent findings show that there is no necessity of large populations of bacteria for the appearance of antibiotic resistance. We know now that small populations of E.coli in an antibiotic gradient can become resistant. Any heterogeneous environment with respect to nutrient and antibiotic gradients may facilitate the development of antibiotic resistance in small bacterial populations and this is also true for the human body. Researchers hypothesize that the mechanism of resistance development is based on four SNP mutations in the genome of E.coli produced by the gradient of antibiotic. These mutations confer the bacteria emergence of antibiotic resistance.
Staphylococcus aureus (colloquially known as "Staph aureus" or a "Staph infection") is one of the major resistant pathogens. Found on the mucous membranes and the human skin of around a third of the population, it is extremely adaptable to antibiotic pressure. It was one of the earlier bacteria in which penicillin resistance was found—in 1947, just four years after the drug started being mass-produced. Methicillin was then the antibiotic of choice, but has since been replaced by oxacillin due to significant kidney toxicity. Methicillin-resistant Staphylococcus aureus (MRSA) was first detected in Britain in 1961, and is now "quite common" in hospitals. MRSA was responsible for 37% of fatal cases of sepsis in the UK in 1999, up from 4% in 1991. Half of all S. aureus infections in the US are resistant to penicillin, methicillin, tetracycline and erythromycin.
This left vancomycin as the only effective agent available at the time. However, strains with intermediate (4-8 μg/ml) levels of resistance, termed glycopeptide-intermediate Staphylococcus aureus (GISA) or vancomycin-intermediate Staphylococcus aureus (VISA), began appearing in the late 1990s. The first identified case was in Japan in 1996, and strains have since been found in hospitals in England, France and the US. The first documented strain with complete (>16 μg/ml) resistance to vancomycin, termed vancomycin-resistant Staphylococcus aureus (VRSA) appeared in the United States in 2002. However, in 2011, a variant of vancomycin has been tested that binds to the lactate variation and also binds well to the original target, thus reinstating potent antimicrobial activity.
A new class of antibiotics, oxazolidinones, became available in the 1990s, and the first commercially available oxazolidinone, linezolid, is comparable to vancomycin in effectiveness against MRSA. Linezolid-resistance in S. aureus was reported in 2001.
Community-acquired MRSA (CA-MRSA) has now emerged as an epidemic that is responsible for rapidly progressive, fatal diseases, including necrotizing pneumonia, severe sepsis, and necrotizing fasciitis. MRSA is the most frequently identified antimicrobial drug-resistant pathogen in US hospitals. The epidemiology of infections caused by MRSA is rapidly changing. In the past 10 years[when?], infections caused by this organism have emerged in the community. The two MRSA clones in the United States most closely associated with community outbreaks, USA400 (MW2 strain, ST1 lineage) and USA300, often contain Panton-Valentine leukocidin (PVL) genes and, more frequently, have been associated with skin and soft tissue infections. Outbreaks of CA-MRSA infections have been reported in correctional facilities, among athletic teams, among military recruits, in newborn nurseries, and among men that have sex with men. CA-MRSA infections now appear endemic in many urban regions and cause most CA-S. aureus infections.
Streptococcus and Enterococcus
Streptococcus pyogenes (Group A Streptococcus: GAS) infections can usually be treated with many different antibiotics. Early treatment may reduce the risk of death from invasive group A streptococcal disease. However, even the best medical care does not prevent death in every case. For those with very severe illness, supportive care in an intensive-care unit may be needed. For persons with necrotizing fasciitis, surgery often is needed to remove damaged tissue. Strains of S. pyogenes resistant to macrolide antibiotics have emerged; however, all strains remain uniformly susceptible to penicillin.
Resistance of Streptococcus pneumoniae to penicillin and other beta-lactams is increasing worldwide. The major mechanism of resistance involves the introduction of mutations in genes encoding penicillin-binding proteins. Selective pressure is thought to play an important role, and use of beta-lactam antibiotics has been implicated as a risk factor for infection and colonization. S. pneumoniae is responsible for pneumonia, bacteremia, otitis media, meningitis, sinusitis, peritonitis and arthritis.
Multidrug-resistant Enterococcus faecalis and Enterococcus faecium are associated with nosocomial infections. Among these strains, penicillin-resistant Enterococcus was seen in 1983, vancomycin-resistant Enterococcus in 1987, and linezolid-resistant Enterococcus in the late 1990s.
Pseudomonas aeruginosa is a highly prevalent opportunistic pathogen. One of the most worrisome characteristics of P. aeruginosa is its low antibiotic susceptibility, which is attributable to a concerted action of multidrug efflux pumps with chromosomally encoded antibiotic resistance genes (for example, mexAB-oprM, mexXY, etc.) and the low permeability of the bacterial cellular envelopes. Pseudomonas aeruginosa has the ability to produce 4-hydroxy-2-alkylquinolines (HAQs) and it has been found that HAQs have prooxidant effects, and overexpressing modestly increased susceptibility to antibiotics. The study experimented with the Pseudomonas aeruginosa biofilms and found that a disruption of relA and spoT genes produced an inactivation of the Stringent response (SR) in cells with nutrient limitation, which provides cells be more susceptible to antibiotics.
C. difficile colitis is most strongly associated with fluoroquinolones, cephalosporins, carbapenems, and clindamycin. The European Center for Disease Prevention and Control recommend that fluoroquinolones and the antibiotic clindamycin be avoided in clinical practice due to their high association with CDI.
Some research suggests the overuse of antibiotics in the raising of livestock is contributing to outbreaks of bacterial infections such as C. difficile.
Antibiotics, especially those with a broad activity spectrum (such as clindamycin) disrupt normal intestinal flora. This can lead to an overgrowth of C. difficile, which flourishes under these conditions. Pseudomembranous colitis can follow, creating generalized inflammation of the colon and the development of "pseudomembrane", a viscous collection of inflammatory cells, fibrin, and necrotic cells. Clindamycin-resistant C. difficile was reported as the causative agent of large outbreaks of diarrheal disease in hospitals in New York, Arizona, Florida and Massachusetts between 1989 and 1992. Geographically dispersed outbreaks of C. difficile strains resistant to fluoroquinolone antibiotics, such as ciprofloxacin and levofloxacin, were also reported in North America in 2005.
Salmonella and E. coli
Infection with Escherichia coli and Salmonella can result from the consumption of contaminated food and water. When both bacteria are spread, serious health conditions arise. Many people are hospitalized each year after becoming infected, with some dying as a result. Since 1993, some strains of E. coli have become resistant to multiple types of fluoroquinolone antibiotics.
On November 5, 2004, the Centers for Disease Control and Prevention (CDC) reported an increasing number of Acinetobacter baumannii bloodstream infections in patients at military medical facilities in which service members injured in the Iraq/Kuwait region during Operation Iraqi Freedom and in Afghanistan during Operation Enduring Freedom were treated. Most of these showed multidrug resistance (MRAB), with a few isolates resistant to all drugs tested.
Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria are a group of emerging highly drug-resistant Gram-negative bacilli causing infections associated with significant morbidity and mortality whose incidence is rapidly increasing in a variety of clinical settings around the world. Klebsiella pneumoniae includes numerous mechanisms for antibiotic resistance, many of which are located on highly mobile genetic elements. Carbapenem antibiotics (heretofore often the treatment of last resort for resistant infections) are generally not effective against KPC-producing organisms.
Tuberculosis is increasing across the globe, especially in developing countries, over the past few years. TB resistant to antibiotics is called MDR TB (Multidrug Resistant TB). Globally, MDR TB causes 150,000 deaths annually. The rise of the HIV/AIDS epidemic has contributed to this.
TB was considered one of the most prevalent diseases, and did not have a cure until the discovery of Streptomycin by Selman Waksman in 1943. However, the bacteria soon developed resistance. Since then, drugs such as isoniazid and rifampin have been used. M. tuberculosis develops resistance to drugs by spontaneous mutations in its genomes. Resistance to one drug is common, and this is why treatment is usually done with more than one drug. Extensively Drug-Resistant TB (XDR TB) is TB that is also resistant to the second line of drugs.
Resistance of Mycobacterium tuberculosis to isoniazid, rifampin, and other common treatments has become an increasingly relevant clinical challenge. (For more on Drug-Resistant TB, visit the Multi-drug-resistant tuberculosis page.)
|This section requires expansion with: information from main article. (November 2013)|
Neisseria gonorrhoeae is a sexually transmitted pathogen that can cause pelvic pain, pain on urination, penile, and vaginal discharge, as well as systemic symptoms in human infection. The bacteria was first identified in 1879, although some Biblical scholars believe that references to the disease can be found as early as Parshat Metzora of the Old Testament.
Treatment with penicillin in the 1940s proved helpful, but by the 1970s resistant strains predominated. Resistance to penicillin has developed through two mechanisms: chomasomally mediated resistance (CMRNG) and penicillinase-mediated resistance (PPNG). CMRNG involves stepwise mutation of penA, which codes for the penicilin-binding protein (PBP-2); mtr, which encodes an efflux pump to remove penicilin from the cell; and penB, which encodes the bacterial cell wall porins. PPNG involves the acquisition of a plasmid-borne beta-lactamase. Fluoroquinolones were a useful next-line treatment until resistance was achieved through efflux pumps and mutations to the gyrA gene, which encodes DNA gyrase. Third-generation cephalosporins have been used to treat gonorrhoea since 2007, although resistant strains have emerged. Strains of Neisseria gonorrhoea have also been found to be resistant to tetracyclines and aminoglycosides. Neisseria gonorrheoea has a high affinity for horizontal gene transfer, and as a result, the existence of any strain resistant to a given drug could spread easily across strains. Today, injectable ceftriaxone is used, sometimes in combination with azithromycin or doxycycline.
World Health Organization recommendations
- People can help tackle resistance by:
- using antibiotics only when prescribed by a doctor;
- completing the full prescription, even if they feel better;
- never sharing antibiotics with others or using leftover prescriptions.
- Health workers and pharmacists can help tackle resistance by:
- enhancing infection prevention and control;
- only prescribing and dispensing antibiotics when they are truly needed;
- prescribing and dispensing the right antibiotic(s) to treat the illness.
- Policymakers can help tackle resistance by:
- strengthening resistance tracking and laboratory capacity;
- regulating and promoting appropriate use of medicines.
- Policymakers and industry can help tackle resistance by:
- fostering innovation and research and development of new tools;
- promoting cooperation and information sharing among all stakeholders.
Rational use of antibiotics may reduce the chances of development of opportunistic infection by antibiotic-resistant bacteria due to dysbacteriosis. Our immune systems will cure minor bacterial infections on their own. If we give it the chance without relying on antibiotics to cure a small infection, it will be less likely to become immune or resistant to the antibiotic. It is also important to note that antibiotics will not cure viral infections such as colds and the flu, and taking an antibiotic unnecessarily to treat a viral infection can lead to the resistance of antibiotics In one study, the use of fluoroquinolones is clearly associated with Clostridium difficile infection, which is a leading cause of nosocomial diarrhea in the United States, and a major cause of death, worldwide.
Vaccines do not have the problem of resistance because a vaccine enhances the body's natural defenses, whereas an antibiotic operates separately from the body's normal defenses. Nevertheless, new strains that escape immunity induced by vaccines may evolve; for example, an updated influenza vaccine is needed each year.
While theoretically promising, antistaphylococcal vaccines have shown limited efficacy, because of immunological variation between Staphylococcus species, and the limited duration of effectiveness of the antibodies produced. Development and testing of more effective vaccines is underway.
The Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO), realizing the need for the reduction of antibiotic use, has been working on two alternatives. One alternative is to prevent diseases by adding cytokines instead of antibiotics to animal feed. These proteins are made in the animal body "naturally" after a disease and are not antibiotics, so they do not contribute to the problem of antibiotic resistance. Furthermore, studies on using cytokines have shown they also enhance the growth of animals like the antibiotics now used, but without the drawbacks of nontherapeutic antibiotic use. Cytokines have the potential to achieve the animal growth rates traditionally sought by the use of antibiotics without the contribution of antibiotic resistance associated with the widespread nontherapeutic uses of antibiotics currently used in the food animal production industries. In addition, CSIRO is working on vaccines for diseases.
Phage therapy, an approach that has been extensively researched and used as a therapeutic agent for over 60 years, especially in the Soviet Union, represents a potentially significant but currently underdeveloped approach to the treatment of bacterial disease. Phage therapy was widely used in the United States until the discovery of antibiotics, in the early 1940s. Bacteriophages or "phages" are viruses that invade bacterial cells and, in the case of lytic phages, disrupt bacterial metabolism and cause the bacterium to lyse. Phage therapy is the therapeutic use of lytic bacteriophages to treat pathogenic bacterial infections.  
Bacteriophage therapy is a potentially important alternative to antibiotics in the current era of multidrug-resistant pathogens. A review of studies that dealt with the therapeutic use of phages from 1966 to 1996 and few latest ongoing phage therapy projects via internet showed: Phages were used topically, orally or systemically in Polish and Soviet studies. The success rate found in these studies was 80–95%, with few gastrointestinal or allergic side-effects. British studies also demonstrated significant efficacy of phages against Escherichia coli, Acinetobacter spp., Pseudomonas spp., and Staphylococcus aureus. US studies dealt with improving the bioavailability of phage. Phage therapy may prove as an important alternative to antibiotics for treating multidrug-resistant pathogens.
Since the discovery of antibiotics, research and development (R&D) efforts have provided new drugs in time to treat bacteria that became resistant to older antibiotics, but in the 2000s there has been concern that development has slowed enough that seriously ill patients may run out of treatment options. Another concern is that doctors may become reluctant to perform routine surgeries due to the increased risk of harmful infection. Backup treatments can have serious side-effects; for example, treatment of multi-drug-resistant tuberculosis can cause deafness and insanity. The potential crisis at hand is the result of a marked decrease in industry R&D. Poor financial investment in antibiotic research has exacerbated the situation. In 2011, Pfizer, one of the last major pharmaceutical companies developing new antibiotics, shut down its primary research effort, citing poor shareholder returns relative to drugs for chronic illnesses.
In the United States, drug companies and the administration of President Barack Obama have been proposing changing the standards by which the FDA approves antibiotics targeted at resistant organisms. On 12 December 2013, the Antibiotic Development to Advance Patient Treatment (ADAPT) Act of 2013 was introduced in the U.S. Congress. The ADAPT Act aims to fast-track the drug development in order to combat the growing public health threat of 'superbugs'. Under this Act, the FDA can approve antibiotics and antifungals needed for life-threatening infections based on data from smaller clinical trials. The CDC will reinforce the monitoring of the use of antibiotics that treat serious and life-threatening infections and the emerging resistance, and make the data publicly available. The FDA antibiotics labeling process, 'Susceptibility Test Interpretive Criteria for Microbial Organisms' or 'breakpoints' is also streamlined to allow the most up-to-date and cutting-edge data available to healthcare professionals under the new Act.
The U.S. National Institutes of Health plans to fund a new research network on the issue up to $62 million from 2013 to 2019. Using authority created by the Pandemic and All Hazards Preparedness Act of 2006, the Biomedical Advanced Research and Development Authority in the U.S. Department of Health and Human Services announced that it will spend between $40 million and $200 million in funding for R&D on new antibiotic drugs under development by GlaxoSmithKline.
In research published on October 17, 2008 in Cell, a team of scientists pinpointed the place on bacteria where the antibiotic myxopyronin launches its attack, and why that attack is successful. The myxopyronin binds to and inhibits the crucial bacterial enzyme RNA polymerase. The myxopyronin changes the structure of the switch-2 segment of the enzyme, inhibiting its function of reading and transmitting DNA code. This prevents RNA polymerase from delivering genetic information to the ribosomes, causing the bacteria to die.
In 2012, a team of the University of Leipzig modified a peptide found in honeybees. It is effective against 37 types of bacteria.
One major cause of antibiotic resistance is the increased pumping activity of microbial ABC transporters, which diminishes the effective drug concentration inside the microbial cell. ABC transporter inhibitors that can be used in combination with current antimicrobials are being tested in clinical trials and are available for therapeutic regimens.
Antibiotic resistance is an important tool for genetic engineering. By constructing a plasmid that contains an antibiotic-resistance gene as well as the gene being engineered or expressed, a researcher can ensure that, when bacteria replicate, only the copies that carry the plasmid survive. This ensures that the gene being manipulated passes along when the bacteria replicates.
In general, the most commonly used antibiotics in genetic engineering are "older" antibiotics that have largely fallen out of use in clinical practice. These include:
In industry, the use of antibiotic resistance is disfavored, since maintaining bacterial cultures would require feeding them large quantities of antibiotics. Instead, the use of auxotrophic bacterial strains (and function-replacement plasmids) is preferred.
- Alliance for the Prudent Use of Antibiotics
- Antibacterial soap
- Beta-lactamase#KPC (K. pneumoniae carbapenemase) (Class A) (KPC) antibacterial resistance gene
- Broad-spectrum antibiotic
- Carbapenem resistant enterobacteriaceae
- Center for Disease Dynamics, Economics & Policy
- Drug of last resort
- Index of environmental articles
- Multidrug tolerance
- Multidrug-resistant gram-negative bacteria
- New Delhi metallo-beta-lactamase (NDM-1) antibacterial resistance gene
- Pesticide resistance
- "Antibiotic Resistance Questions & Answers". Get Smart: Know When Antibiotics Work. Centers for Disease Control and Prevention, USA. 30 June 2009. Retrieved 20 March 2013.
- "WHO's first global report on antibiotic resistance reveals serious, worldwide threat to public health" Retrieved 2014-05-02
- Zainuddin ZF, Dale JW (1990). "Does Mycobacterium tuberculosis have plasmids?". Tubercle 71 (1): 43–9. doi:10.1016/0041-3879(90)90060-l. PMID 2115217.
- Louw GE, Warren RM, Gey van Pittius NC, McEvoy CR, Van Helden PD, Victor TC (2009). "A Balancing Act: Efflux/Influx in Mycobacterial Drug Resistance". Antimicrobial Agents and Chemotherapy 53 (8): 3181–9. doi:10.1128/AAC.01577-08. PMC 2715638. PMID 19451293.
- D'Costa et al. 2011, pp. 457–461.
- Donadio et al. 2010, pp. 423–430.
- Caldwell & Lindberg 2011.
- Nelson 2009, p. 294.
- Hawkey & Jones 2009, pp. i3-i10.
- Goossens H, Ferech M, Vander Stichele R, Elseviers M (2005). "Outpatient antibiotic use in Europe and association with resistance: a cross-national database study". Lancet 365 (9459): 579–87. doi:10.1016/S0140-6736(05)17907-0. PMID 15708101.
- Ferber D (4 January 2002). "Livestock Feed Ban Preserves Drugs' Power". Science 295 (5552): 27–28. doi:10.1126/science.295.5552.27a. PMID 11778017.
- Mathew AG, Cissell R, Liamthong S; Cissell, R; Liamthong, S (2007). "Antibiotic resistance in bacteria associated with food animals: a United States perspective of livestock production". Foodborne Pathog. Dis. 4 (2): 115–33. doi:10.1089/fpd.2006.0066. PMID 17600481.
- CDC. "Antibiotic Resistance Questions & Answers" [Are antibacterial-containing products (soaps, household cleaners, etc.) better for preventing the spread of infection? Does their use add to the problem of resistance?]. Atlanta, Georgia, USA.: Centers for Disease Control and Prevention. Archived from the original on 8 November 2009. Retrieved November 17, 2009.
- Larsson DG, Fick J (Jan 2009). "Transparency throughout the production chain -- a way to reduce pollution from the manufacturing of pharmaceuticals?". Regul Toxicol Pharmacol 53 (3): 161–3. doi:10.1016/j.yrtph.2009.01.008. PMID 19545507.
- Healthcare-associated Infections
- "Antibiotic resistance". Sciencedaily.com. Retrieved 2013-06-12.
- Tacconelli E, De Angelis G, Cataldo MA, Pozzi E, Cauda R (January 2008). "Does antibiotic exposure increase the risk of methicillin-resistant Staphylococcus aureus (MRSA) isolation? A systematic review and meta-analysis". J. Antimicrob. Chemother. 61 (1): 26–38. doi:10.1093/jac/dkm416. PMID 17986491.
- Muto CA, Jernigan JA, Ostrowsky BE, Richet HM, Jarvis WR, Boyce JM, Farr BM (May 2003). "SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and enterococcus". Infect Control Hosp Epidemiol 24 (5): 362–86. doi:10.1086/502213. PMID 12785411.
- Vonberg, Dr Ralf-Peter. "Clostridium difficile: a challenge for hospitals". European Center for Disease Prevention and Control. Institute for Medical Microbiology and Hospital Epidemiology: IHE. Archived from the original on 11 June 2009. Retrieved 27 July 2009.
- Kuijper EJ, van Dissel JT, Wilcox MH; van Dissel, J.; Wilcox, MH (Aug 2007). "Clostridium difficile: changing epidemiology and new treatment options". Current Opinion in Infectious Diseases 20 (4): 376–83. doi:10.1097/QCO.0b013e32818be71d. PMID 17609596.
- editors, Ronald Eccles, Olaf Weber, (2009). Common cold (Online-Ausg. ed.). Basel: Birkhäuser. p. 240. ISBN 978-3-7643-9894-1.
- Martin Khor (2014-05-18). "Why Are Antibiotics Becoming Useless All Over the World?". The Real News. Retrieved 2014-05-18.
- Wright GD (October 2010). "Antibiotic resistance in the environment: a link to the clinic?". Current Opinion in Microbiology 13 (5): 589–94. doi:10.1016/j.mib.2010.08.005. PMID 20850375.
- "Mutations are random". University of California. Retrieved Aug 14, 2011.
- Richard William Nelson. Darwin, Then and Now: The Most Amazing Story in the History of Science, iUniverse, 2009, p. 294
- Wayne W. Umbreit, Advances in Applied Microbiology, vol. 11, Academic Press, 1970, p. 80
- Pollock MR (1967). "Origin and function of penicillinase: a problem in biochemical evolution". British Medical Journal 4 (5571): 71–7. doi:10.1136/bmj.4.5571.71. PMC 1748446. PMID 4963324.
- New Scientist, Jun 8, 1972, p. 546
- New Scientist, Feb 11, 1989, p. 34
- Pollock, p. 77
- Abigail A. Salyers, Dixie D. Whitt. Revenge of the microbes: how bacterial resistance is undermining the antibiotic miracle, ASM Press, 2005, p. 34
- Pechère JC (September 2001). "Patients' interviews and misuse of antibiotics". Clin. Infect. Dis. 33 Suppl 3: S170–3. doi:10.1086/321844. PMID 11524715.
- Arnold SR, Straus SE; Straus, SE (2005). "Interventions to improve antibiotic prescribing practices in ambulatory care". In Arnold, Sandra R. Cochrane Database of Systematic Reviews (4): CD003539. doi:10.1002/14651858.CD003539.pub2. PMID 16235325.
- McNulty CA, Boyle P, Nichols T, Clappison P, Davey P (August 2007). "The public's attitudes to and compliance with antibiotics". J. Antimicrob. Chemother. 60 Suppl 1: i63–8. doi:10.1093/jac/dkm161. PMID 17656386.
- editors, Ronald Eccles, Olaf Weber, (2009). Common cold (Online-Ausg. ed.). Basel: Birkhäuser. p. 234. ISBN 978-3-7643-9894-1.
- Costelloe C, Metcalfe C, Lovering A, Mant D, Hay AD (2010). "Effect of antibiotic prescribing in primary care on antimicrobial resistance in individual patients: systematic review and meta-analysis". British Medical Journal 340: c2096. doi:10.1136/bmj.c2096. PMID 20483949.
- Li JZ, Winston LG, Moore DH, Bent S (September 2007). "Efficacy of short-course antibiotic regimens for community-acquired pneumonia: a meta-analysis". Am. J. Med. 120 (9): 783–90. doi:10.1016/j.amjmed.2007.04.023. PMID 17765048.
- Bignardi GE (31 August 1998). "Risk factors for Clostridium difficile infection". Journal of Hospital Infection 40 (1): 1–15. doi:10.1016/S0195-6701(98)90019-6. PMID 9777516.
- Runyon BA, McHutchison JG, Antillon MR, Akriviadis EA, Montano AA (June 1991). "Short-course versus long-course antibiotic treatment of spontaneous bacterial peritonitis. A randomized controlled study of 100 patients". Gastroenterology 100 (6): 1737–42. PMID 2019378.
- Singh N, Rogers P, Atwood CW, Wagener MM, Yu VL (1 August 2000). "Short-course Empiric Antibiotic Therapy for Patients with Pulmonary Infiltrates in the Intensive Care Unit A Proposed Solution for Indiscriminate Antibiotic Prescription". Am. J. Respir. Crit. Care Med. 162 (2): 505–511. doi:10.1164/ajrccm.162.2.9909095. PMID 10934078.
- Gleisner AL, Argenta R, Pimentel M, Simon TK, Jungblut CF, Petteffi L, de Souza RM, Sauerssig M, Kruel CD, Machado AR (30 April 2004). "Infective complications according to duration of antibiotic treatment in acute abdomen". International Journal of Infectious Diseases 8 (3): 155–162. doi:10.1016/j.ijid.2003.06.003. PMID 15109590.
- Pichichero ME, Cohen R (1997). "Shortened course of antibiotic therapy for acute otitis media, sinusitis and tonsillopharyngitis". The Pediatric Infectious Disease Journal 16 (7): 680–95. doi:10.1097/00006454-199707000-00011. PMID 9239773.
- Dellinger EP, Wertz MJ, Lennard ES, Oreskovich MR (1986). "Efficacy of Short-Course Antibiotic Prophylaxis After Penetrating Intestinal Injury". Archives of Surgery 121 (1): 23–30. doi:10.1001/archsurg.1986.01400010029002. PMID 3942496.
- Perez-Gorricho B, Ripoll M (2003). "Does short-course antibiotic therapy better meet patient expectations?". International Journal of Antimicrobial Agents 21 (3): 222–8. doi:10.1016/S0924-8579(02)00360-6. PMID 12636982.
- Keren R, Chan E (2002). "A Meta-analysis of Randomized, Controlled Trials Comparing Short- and Long-Course Antibiotic Therapy for Urinary Tract Infections in Children". Pediatrics 109 (5): E70–0. doi:10.1542/peds.109.5.e70. PMID 11986476.
- McCormack J, Allan GM (2012). "A prescription for improving antibiotic prescribing in primary care". British Medical Journal 344: d7955. doi:10.1136/bmj.d7955. PMID 22302779.
- Marc Bonten, MD; Eijkman-Winkler Institute for Medical Microbiology, Infectious Diseases, and Inflammation; Utrecht, the Netherland | http://hicsigwiki.asid.net.au/images/4/41/Should_you_stop_an_antibiotic_course_early_if_you_feel_better_R._Everts.pdf
- Thomas JK, Forrest A, Bhavnani SM, Hyatt JM, Cheng A, Ballow CH, Schentag JJ (March 1998). "Pharmacodynamic Evaluation of Factors Associated with the Development of Bacterial Resistance in Acutely Ill Patients during Therapy". Antimicrob. Agents Chemother. 42 (3): 521–7. PMC 105492. PMID 9517926.
- Girou E, Legrand P, Soing-Altrach S, Lemire A, Poulain C, Allaire A, Tkoub-Scheirlinck L, Chai SH, Dupeyron C, Loche CM (October 2006). "Association between hand hygiene compliance and methicillin-resistant Staphylococcus aureus prevalence in a French rehabilitation hospital". Infect Control Hosp Epidemiol 27 (10): 1128–30. doi:10.1086/507967. PMID 17006822.
- Swoboda SM, Earsing K, Strauss K, Lane S, Lipsett PA (February 2004). "Electronic monitoring and voice prompts improve hand hygiene and decrease nosocomial infections in an intermediate care unit". Crit. Care Med. 32 (2): 358–63. doi:10.1097/01.CCM.0000108866.48795.0F. PMID 14758148.
- Farmer, Paul E., Bruce Nizeye, Sara Stulac, and Salmaan Keshavjee. 2006. Structural Violence and Clinical Medicine. PLoS Medicine, 1686–1691.
- The Resistance Phenomenon in Microbes and Infectious Disease Vectors: Implications for Human Health and Strategies for Containment: Workshop Summary. Institute of Medicine (US) Forum on Emerging Infections; Knobler SL, Lemon SM, Najafi M, et al., editors. Washington (DC): National Academies Press (US); 2003.
- Hersom, Matt. "Application of Ionophores in Cattle Diets". AN285 Department of Animal Sciences. University of Florida IFAS Extension. Retrieved 14 March 2013.
- The Editorial Board of the New York Times, May 10, 2014, The Rise of Antibiotic Resistance
- Schneider, K; Garrett, L (June 19, 2009). "Non-therapeutic Use of Antibiotics in Animal Agriculture, Corresponding Resistance Rates, and What Can be Done About It". Center for Global Development.
- Hurd HS, Doores S, Hayes D, Mathew A, Maurer J, Silley P, Singer RS, Jones RN (2004). "Public health consequences of macrolide use in food animals: a deterministic risk assessment". J. Food Prot. 67 (5): 980–92. PMID 15151237.
- Hurd HS, Malladi S (2008). "A stochastic assessment of the public health risks of the use of macrolide antibiotics in food animals". Risk Anal. 28 (3): 695–710. doi:10.1111/j.1539-6924.2008.01054.x. PMID 18643826.
- Joint FAO/OIE/WHO Expert Workshop on Non-Human Antimicrobial Usage and Antimicrobial Resistance: Scientific assessment 
- OIE, Terrestrial Animal Health Code
- OIE,Terrestrial Animal Health Code
- OIE,Terrestrial Animal Health Code
- Castanon JI (2007). "History of the use of antibiotic as growth promoters in European poultry feeds". Poult. Sci. 86 (11): 2466–71. doi:10.3382/ps.2007-00249. PMID 17954599.
- Bengtsson B, Wierup M; Wierup, M. (2006). "Antimicrobial resistance in Scandinavia after ban of antimicrobial growth promoters". Anim. Biotechnol. 17 (2): 147–56. doi:10.1080/10495390600956920. PMID 17127526.
- "GAO-11-801, Antibiotic Resistance: Agencies Have Made Limited Progress Addressing Antibiotic Use in Animals". gao.gov. Retrieved 2014-01-25.
- Sapkota AR, Lefferts LY, McKenzie S, Walker P (May 2007). "What Do We Feed to Food-Production Animals? A Review of Animal Feed Ingredients and Their Potential Impacts on Human Health". Environ. Health Perspect. 115 (5): 663–70. doi:10.1289/ehp.9760. PMC 1867957. PMID 17520050.
- Baker R (2006). "Health management with reduced antibiotic use — the U.S. experience". Anim. Biotechnol. 17 (2): 195–205. doi:10.1080/10495390600962274. PMID 17127530.
- "Executive summary from the UCS report "Hogging It: Estimates of Antimicrobial Abuse in Livestock"". Union of Concerned Scientists. January 2001.
- Nelson JM, Chiller TM, Powers JH, Angulo FJ (Apr 2007). "Fluoroquinolone-resistant Campylobacter species and the withdrawal of fluoroquinolones from use in poultry: a public health success story". Clin Infect Dis 44 (7): 977–80. doi:10.1086/512369. PMID 17342653.
- APHIS. "Clostridium difficile on U.S. Swine Operations". Retrieved 24 October 2013.
- "US Senate Bill S. 549: Preservation of Antibiotics for Medical Treatment Act of 2007".
- "Preservation of Antibiotics for Medical Treatment Act of 2007".
- John Gever (March 23, 2012). "FDA Told to Move on Antibiotic Use in Livestock". MedPage Today. Retrieved March 24, 2012.
- Gardiner Harris (April 11, 2012). "U.S. Tightens Rules on Antibiotics Use for Livestock". The New York Times. Retrieved April 12, 2012.
- "FDA's Strategy on Antimicrobial Resistance — Questions and Answers". U.S. Food and Drug Administration. April 11, 2012. Retrieved April 12, 2012. "“Judicious use” is using an antimicrobial drug appropriately and only when necessary; Based on a thorough review of the available scientific information, FDA recommends that use of medically important antimicrobial drugs in food-producing animals be limited to situations where the use of these drugs is necessary for ensuring animal health, and their use includes veterinary oversight or consultation. FDA believes that using medically important antimicrobial drugs to increase production in food-producing animals is not a judicious use."
- Tavernise, Sabrina. "F.D.A. to Phase Out Use of Some Antibiotics in Animals Raised for Meat". The New York Times. Retrieved 11 December 2013.
- Martinez, J. L., & Olivares, J. (2012). Envrironmental Pollution By Antibiotic Resistance Genes. In P. L. Keen, & M. H. Montforts, Antimicrobial Resistance in the Environment (pp. 151- 171). Hoboken, N.J.: John Wiley & Sons.
- Pruden, A., & Arabi, M. (2012). Quantifying Anthropogenic Impacts on Environmental Reservoirs of Antibiotic Resistance. In P. L. Keen, & M. H. Montforts, Antimicrobial Resistance in the Environment (pp. 173-202). Hoboken, N.J.: John Wiley & Sons.
- Ochiai, K.; Yamanaka, T; Kimura, K; Sawada, O (1959). "Inheritance of drug resistance (and its transfer) between Shigella strains and Between Shigella and E.coli strains". Hihon Iji Shimpor, (in Japanese) 34: 1861.
- Li XZ, Nikaido H; Nikadio, H (2009). "Efflux-Mediated Drug Resistance in Bacteria: an Update". Drug 69 (12): 1555–623. doi:10.2165/11317030-000000000-00000. PMC 2847397. PMID 19678712.
- Morita Y, Kodama K, Shiota S, Mine T, Kataoka A, Mizushima T, Tsuchiya T (July 1998). "NorM, a Putative Multidrug Efflux Protein, of Vibrio parahaemolyticus and Its Homolog in Escherichia coli". Antimicrob. Agents Chemother. 42 (7): 1778–82. PMC 105682. PMID 9661020.
- Robicsek A, Jacoby GA, Hooper DC; Jacoby, GA; Hooper, DC (October 2006). "The worldwide emergence of plasmid-mediated quinolone resistance". Lancet Infect Dis 6 (10): 629–40. doi:10.1016/S1473-3099(06)70599-0. PMID 17008172.
- Cirz RT, Chin JK, Andes DR, de Crécy-Lagard V, Craig WA, Romesberg FE (2005). "Inhibition of Mutation and Combating the Evolution of Antibiotic Resistance". PLoS Biol. 3 (6): e176. doi:10.1371/journal.pbio.0030176. PMC 1088971. PMID 15869329.
- Chan CX, Beiko RG, Ragan MA; Beiko, RG; Ragan, MA (August 2011). "Lateral Transfer of Genes and Gene Fragments in Staphylococcus Extends beyond Mobile Elements". J Bacteriol 193 (15): 3964–3977. doi:10.1128/JB.01524-10. PMC 3147504. PMID 21622749.
- "CDC: Get Smart: Know When Antibiotics Work". Cdc.gov. Retrieved 2013-06-12.
- "APUA: General Background: Antibiotic Resistance, A Societal Problem". Tufts.edu. Retrieved 2013-06-12.
- Bozdogan B, Esel D, Whitener C, Browne FA, Appelbaum PC (2003). "Antibacterial susceptibility of a vancomycin-resistant Staphylococcus aureus strain isolated at the Hershey Medical Center". Journal of Antimicrobial Chemotherapy 52 (5): 864–868. doi:10.1093/jac/dkg457. PMID 14563898.
- Xie J, Pierce JG, James RC, Okano A, Boger DL (2011). "A Redesigned Vancomycin Engineered for Dual d-Ala-d-Ala and d-Ala-d-Lac Binding Exhibits Potent Antimicrobial Activity Against Vancomycin-Resistant Bacteria". J. Am. Chem. Soc. 133, 133 (35): 13946–9. doi:10.1021/ja207142h. PMC 3164945. PMID 21823662.
- Tsiodras S, Gold HS, Sakoulas G, Eliopoulos GM, Wennersten C, Venkataraman L, Moellering RC, Ferraro MJ. "Linezolid resistance in a clinical isolate of Staphylococcus aureus". The Lancet 358 (9277): 207–208. doi:10.1016/S0140-6736(01)05410-1. PMID 11476839.
- Boyle-Vavra S, Daum RS; Daum, RS (2007). "Community-acquired methicillin-resistant Staphylococcus aureus: the role of Panton-Valentine leukocidin". Lab. Invest. 87 (1): 3–9. doi:10.1038/labinvest.3700501. PMID 17146447.
- Maree CL, Daum RS, Boyle-Vavra S, Matayoshi K, Miller LG (2007). "Community-associated Methicillin-resistant Staphylococcus aureus Isolates and Healthcare-Associated Infections". Emerging Infect. Dis. 13 (2): 236–42. doi:10.3201/eid1302.060781. PMC 2725868. PMID 17479885.
- CDCP (2005-10-11). "Group A Streptococcal (GAS) Disease (strep throat, necrotizing fasciitis, impetigo) -- Frequently Asked Questions". Centers for Disease Control and Prevention. Archived from the original on 19 December 2007. Retrieved 2007-12-11.
- Albrich WC, Monnet DL, Harbarth S; Monnet, DL; Harbarth, S (2004). "Antibiotic selection pressure and resistance in Streptococcus pneumoniae and Streptococcus pyogenes". Emerging Infect. Dis. 10 (3): 514–7. doi:10.3201/eid1003.030252. PMC 3322805. PMID 15109426.
- Hidron AI, Edwards JR, Patel J, Horan TC, Sievert DM, Pollock DA, Fridkin SK (November 2008). "NHSN annual update: antimicrobial-resistant pathogens associated with healthcare-associated infections: annual summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2006-2007". Infect Control Hosp Epidemiol 29 (11): 996–1011. doi:10.1086/591861. PMID 18947320.
- Poole K (2004). "Efflux-mediated multiresistance in Gram-negative bacteria". Clinical Microbiology and Infection 10 (1): 12–26. doi:10.1111/j.1469-0691.2004.00763.x. PMID 14706082.
- Nguyen D, Joshi-Datar A, Lepine F, Bauerle E, Olakanmi O, Beer K, McKay G, Siehnel R, Schafhauser J, Wang Y, Britigan BE, Singh PK (2011). "Active Starvation Responses Mediate Antibiotic Tolerance in Biofilms and Nutrient-Limited Bacteria". Science 334 (6058): 982–6. doi:10.1126/science.1211037. PMID 22096200.
- Gerding DN, Johnson S, Peterson LR, Mulligan ME, Silva J (1995). "Clostridium difficile-associated diarrhea and colitis". Infect. Control. Hosp. Epidemiol. 16 (8): 459–477. doi:10.1086/648363. PMID 7594392.
- McDonald LC (2005). "Clostridium difficile: responding to a new threat from an old enemy". Infect. Control. Hosp. Epidemiol. 26 (8): 672–5. doi:10.1086/502600. PMID 16156321.
- Baxter R, Ray GT, Fireman BH (January 2008). "Case-control study of antibiotic use and subsequent Clostridium difficile-associated diarrhea in hospitalized patients". Infection Control and Hospital Epidemiology : The Official Journal of the Society of Hospital Epidemiologists of America 29 (1): 44–50. doi:10.1086/524320. PMID 18171186.
- Gifford AH, Kirkland KB (December 2006). "Risk factors for Clostridium difficile-associated diarrhea on an adult hematology-oncology ward". European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology 25 (12): 751–5. doi:10.1007/s10096-006-0220-1. PMID 17072575.
- Palmore TN, Sohn S, Malak SF, Eagan J, Sepkowitz KA (August 2005). "Risk factors for acquisition of Clostridium difficile-associated diarrhea among outpatients at a cancer hospital". Infection Control and Hospital Epidemiology : The Official Journal of the Society of Hospital Epidemiologists of America 26 (8): 680–4. doi:10.1086/502602. PMID 16156323.
- Johnson S, Samore MH, Farrow KA, Killgore GE, Tenover FC, Lyras D, Rood JI, DeGirolami P, Baltch AL, Rafferty ME, Pear SM, Gerding DN (1999). "Epidemics of diarrhea caused by a clindamycin-resistant strain of Clostridium difficile in four hospitals". New England Journal of Medicine 341 (23): 1645–1651. doi:10.1056/NEJM199911253412203. PMID 10572152.
- Loo VG, Poirier L, Miller MA, Oughton M, Libman MD, Michaud S, Bourgault AM, Nguyen T, Frenette C, Kelly M, Vibien A, Brassard P, Fenn S, Dewar K, Hudson TJ, Horn R, René P, Monczak Y, Dascal A (2005). "A predominantly clonal multi-institutional outbreak of Clostridium difficile-associated diarrhea with high morbidity and mortality". N Engl J Med 353 (23): 2442–9. doi:10.1056/NEJMoa051639. PMID 16322602.
- "Acinetobacter baumannii infections among patients at military medical facilities treating injured U.S. service members, 2002-2004". MMWR Morb. Mortal. Wkly. Rep. (Centers for Disease Control and Prevention (CDC)) 53 (45): 1063–6. 2004. PMID 15549020.
- "Medscape abstract on Acinetobacter baumannii: Acinetobacter baumannii: An Emerging Multidrug-resistant Threat". "membership only website"
- Hudson, Corey; Bent, Zachary; Meagher, Robert; Williams, Kelly (June 7, 2014). "Resistance Determinants and Mobile Genetic Elements of an NDM-1-Encoding Klebsiella pneumoniae Strain". PLoS ONE. doi:10.1371/journal.pone.0099209.
- Arnold RS, Thom KA, Sharma S, Phillips M, Kristie Johnson J, Morgan DJ (2011). "Emergence of Klebsiella pneumoniae Carbapenemase-Producing Bacteria". Southern Medical Journal 104 (1): 40–5. doi:10.1097/SMJ.0b013e3181fd7d5a. PMC 3075864. PMID 21119555.
- "Antimicrobial Resistance Still Poses a Public Health Threat: A Conversation With Edward J. Septimus, MD, FIDSA, FACP, FSHEA, Clinical Professor of Internal Medicine at Texas A&M Health Science Center". Agency for Healthcare Research and Quality. 2013-04-17. Retrieved 2013-09-26.
- LoBue P (2009). "Extensively drug-resistant tuberculosis". Current Opinion in Infectious Diseases 22 (2): 167–73. doi:10.1097/QCO.0b013e3283229fab. PMID 19283912.
- Herzog H (1998). "History of Tuberculosis". Respiration 65 (1): 5–15. doi:10.1159/000029220. PMID 9523361.
- Gao, Qian; Li, Xia (2010). "Transmission of MDR tuberculosis". Drug Discovery Today: Disease Mechanisms 7: e61. doi:10.1016/j.ddmec.2010.09.006.
- Ligon, B. Lee (October 2005). "Albert Ludwig Sigesmund Neisser: Discoverer of the Cause of Gonorrhea". Seminars in Pediatric Infectious Diseases 16 (4): 336–341. doi:10.1053/j.spid.2005.07.001.
- Rosner, Fred (1995). Medicine in the Bible and the Talmud : selections from classical Jewish sources (Augm. ed. ed.). Hoboken, NJ: KTAV Pub. House. ISBN 0-88125-506-8.
- Tapsall (2001) Antimicrobial resistance in Niesseria gonorrhoeae. World Health Organization.
- Deguchi T, Nakane K, Yasuda M, Maeda S (September 2010). "Emergence and spread of drug resistant Neisseria gonorrhoeae". J. Urol. 184 (3): 851–8; quiz 1235. doi:10.1016/j.juro.2010.04.078. PMID 20643433.
- "Update to CDC's Sexually Transmitted Diseases Treatment Guidelines, 2010: Oral Cephalosporins No Longer a Recommended Treatment for Gonococcal Infections.". MMWR. Morbidity and mortality weekly report 61 (31): 590–4. Aug 10, 2012. PMID 22874837.
- "Evolution of Antibiotic Resistance". PBS.org. WGBH Educational Foundation and Clear Blue Sky Productions, Inc. Retrieved 11 June 2013.
- McCusker ME, Harris AD, Perencevich E, Roghmann MC (2003). "Fluoroquinolone Use and Clostridium difficile–Associated Diarrhea". Emerging Infect. Dis. 9 (6): 730–3. doi:10.3201/eid0906.020385. PMC 3000134. PMID 12781017.
- Frost F, Craun GF, Calderon RL; Craun, GF; Calderon, RL (1998). "Increasing hospitalization and death possibly due to Clostridium difficile diarrheal disease". Emerging Infect. Dis. 4 (4): 619–25. doi:10.3201/eid0404.980412. PMC 2640242. PMID 9866738.
- "Immunity, Infectious Diseases,and Pandemics—What You Can Do". HomesteadSchools.com. Retrieved 2013-06-12.
- "Science,Technology,genetics,research on biotechnology: December 2009". Biotechnolo.blogspot.com. Retrieved 2013-06-12.
- Keen EC (2012). "Phage therapy: concept to cure". Front Microbiol 3: 238. doi:10.3389/fmicb.2012.00238. PMC 3400130. PMID 22833738.
- Chanishvili, N; Chanishvili, T; Tediashvili, M.; Barrow, P.A. (2001). "Phages and their application against drug-resistant bacteria". J. Chem. Technol. Biotechnol. 76 (7): 689–699. doi:10.1002/jctb.438.
- Jikia D, Chkhaidze N, Imedashvili E, Mgaloblishvili I, Tsitlanadze G, Katsarava R, Glenn Morris J, Sulakvelidze A (2005). "The use of a novel biodegradable preparation capable of the sustained release of bacteriophages and ciprofloxacin, in the complex treatment of multidrug-resistant Staphylococcus aureus-infected local radiation injuries caused by exposure to Sr90". Clinical & Experimental Dermatology 30 (1): 23–6. doi:10.1111/j.1365-2230.2004.01600.x. PMID 15663496.
- Weber-Dabrowska B, Mulczyk M, Górski A (June 2003). "Bacteriophages as an efficient therapy for antibiotic-resistant septicemia in man". Transplant. Proc. 35 (4): 1385–6. doi:10.1016/S0041-1345(03)00525-6. PMID 12826166.
- Chowdhry S, Pandhi D, Vidhani S, Bhalla P, Reddy BS (2003). "Bacteriophage therapy: an alternative to conventional antibiotics". J Assoc Physicians India 51 (8): 593–6. doi:10.1258/095646202760159701. PMID 12194741.
- Scientists discover possible antibiotics alternative - Australian Broadcasting Corporation — Retrieved 29 July 2012.
- CMO Annual Report
- Obama Administration Seeks To Ease Approvals For Antibiotics : Shots - Health News : NPR
- Moldova Grapples With Whether To Isolate TB Patients : NPR
- Walsh, Fergus. "BBC News — Antibiotics resistance 'as big a risk as terrorism' - medical chief". Bbc.co.uk. Retrieved 2013-03-12.
- Gever, John (2011-02-04). "Pfizer Moves May Dim Prospect for New Antibiotics". MedPage Today. Retrieved 2013-03-12.
- Ledford H (2012). "FDA under pressure to relax drug rules". Nature 492 (7427): 19. doi:10.1038/492019a. PMID 23222585.
- Press Release (12 December 2013). "Green, Gingrey Introduce ADAPT Act to Safeguard Public Health". U.S. Congress.
- "Antibiotic Development to Advance Patient Treatment Act of 2013". U.S. Congress. 12 December 2013.
- NIH to fund clinical research network on antibacterial resistance
- Mukhopadhyay J, Das K, Ismail S, Koppstein D, Jang M, Hudson B, Sarafianos S, Tuske S, Patel J, Jansen R, Irschik H, Arnold E, Ebright RH (2008). "The RNA polymerase "switch region" is a target for inhibitors". Cell 135 (2): 295–307. doi:10.1016/j.cell.2008.09.033. PMC 2580802. PMID 18957204.
- "Modified Bee Peptide Slays Deadly Bacteria | Chemical & Engineering News". Cen.acs.org. 2012-05-29. Retrieved 2013-03-12.
- Ponte-Sucre, A, ed. (2009). ABC Transporters in Microorganisms. Caister Academic Press. ISBN 978-1-904455-49-3.[page needed]
- Caldwell, Roy; Lindberg, David, eds. (2011). "Understanding Evolution" [Mutations are random]. University of California Museum of Paleontology. Retrieved Aug 14, 2011.
- Nelson, Richard William (2009). Darwin, Then and Now: The Most Amazing Story in the History of Science (Self Published). iUniverse. p. 294.
- Arias CA, Murray BE; Murray, BE (2009). "Antibiotic-Resistant Bugs in the 21st Century — A Clinical Super-Challenge". New England Journal of Medicine 360 (5): 439–443. doi:10.1056/NEJMp0804651. PMID 19179312.
- D'Costa, Vanessa; King, Christine; Kalan, Lindsay; Morar, Mariya; Sung, Wilson; Schwarz, Carsten; Froese, Duane; Zazula, Grant; Calmels, Fabrice; Debruyne, Regis; Golding, G. Brian; Poinar, Hendrik N.; Wright, Gerard D. (September 2011). "Antibiotic resistance is ancient". Nature 477 (7365): 457–461. Bibcode:2011Natur.477..457D. doi:10.1038/nature10388. PMID 21881561.
- Donadio, Stefano; Maffioli, Sonia; Monciardini, Paolo; Sosio, Margherita; Jabes, Daniela (August 2010). "Antibiotic discovery in the twenty-first century: Current trends and future perspectives". The Journal of Antibiotics 63 (8): 423–430. doi:10.1038/ja.2010.62. PMID 20551985.
- Goossens H, Ferech M, Vander Stichele R, Elseviers M; Ferech, M; Vander Stichele, R; Elseviers, M; Esac Project, Group (2005). "Outpatient antibiotic use in Europe and association with resistance: a cross-national database study". Lancet. Group Esac Project 365 (9459): 579–87. doi:10.1016/S0140-6736(05)17907-0. PMID 15708101.
- Hawkey, PM; Jones, AM (September 2009). "The changing epidemiology of resistance". The Journal of antimicrobial chemotherapy. 64 Suppl 1: i3–10. doi:10.1093/jac/dkp256. PMID 19675017.
- Soulsby EJ (2005). "Resistance to antimicrobials in humans and animals: Overusing antibiotics is not the only cause and reducing use is not the only solution". British Medical Journal 331 (7527): 1219–20. doi:10.1136/bmj.331.7527.1219. PMC 1289307. PMID 16308360.
- "Alternatives to Antibiotics Reduce Animal Disease". Commonwealth Scientific and Industrial Research Organization. 9 Jan 2006.
- Animation of Antibiotic Resistance
- CDC Article on Hospital Acquired MRSA
- CDC Article on Community Acquired MRSA
- CDC Guideline "Management of Multidrug-Resistant Organisms in Healthcare Settings, 2006"
- ReAct Action on Antibiotic Resistance
- Alliance for the Prudent Use of Antibiotics
- Cox LA, Popken DA (2006). "Quantifying Potential Human Health Impacts of Animal Antibiotic Use: Enrofloxacin and Macrolides in Chickens". Risk Analysis 26 (1): 135–146. doi:10.1111/j.1539-6924.2006.00723.x. PMID 16492187.
- Information about phage therapy – a possible alternative to antibiotics in case of resistant infections
- Antibiotic-resistance genes as markers Once necessary, now undesirable
- CBS Article on Phage Therapy and Antibiotic Resistance
- Hospitals: Breeding the Superbug Article on MRSA infections in hospitals, Allianz Knowledge, by Valdis Wish, May 2008.
- BURDEN of Resistance and Disease in European Nations - An EU-Project to estimate the financial burden of antibiotic resistance in European Hospitals
- Extending the Cure: Policy Research to Extend Antibiotic Effectiveness
- 2003 New Guidance for Industry on Antimicrobial Drugs for Food Animals Questions and Answers, U.S. FDA
- SciDev.net Antibiotic Resistance spotlight The Science and Development Network is an online science and development network focused on news and information important to the developing world
- Do Bugs Need Drugs?
- Combating Drug Resistance - Tackling drug resistance in bacteria and other pathogens.
-  Nanoparticles could treat antibiotic resistant infections.