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Bacteremia (also bacteraemia) is the presence of bacteria in the blood. Blood is normally a sterile environment, so the detection of bacteria in the blood (most commonly accomplished by blood cultures) is always abnormal. It is distinct from sepsis, which is the host response to the bacteria.
Bacteria can enter the bloodstream as a severe complication of infections (like pneumonia or meningitis), during surgery (especially when involving mucous membranes such as the gastrointestinal tract), or due to catheters and other foreign bodies entering the arteries or veins (including during intravenous drug abuse). Transient bacteremia can result after dental procedures or brushing of teeth.
Bacteremia can have several important health consequences. The immune response to the bacteria can cause sepsis and septic shock, which has a high mortality rate. Bacteria can also spread via the blood to other parts of the body (which is called hematogenous spread), causing infections away from the original site of infection, such as endocarditis or osteomyelitis. Treatment for bacteremia is with antibiotics, and prevention with antibiotic prophylaxis can be given in high risk situations.
Bacteremia is the presence of bacteria in the bloodstream that are alive and capable of reproducing. It is a type of bloodstream infection. Bacteremia is defined as either a primary or secondary process. In primary bacteremia, bacteria have been directly introduced into the bloodstream. Injection drug use may lead to primary bacteremia. In the hospital setting, use of blood vessel catheters contaminated with bacteria may also lead to primary bacteremia. Secondary bacteremia occurs when bacteria have entered the body at another site, such as the cuts in the skin, or the mucous membranes of the lungs (respiratory tract), mouth or intestines (gastrointestinal tract), bladder (urinary tract), or genitals. Bacteria that have infected the body at these sites may then spread into the lymphatic system and gain access to the bloodstream, where further spread can occur.
Bacteremia may also be defined by the timing of bacteria presence in the bloodstream: transient, intermittent, or persistent. In transient bacteremia, bacteria are present in the bloodstream for minutes to a few hours before being cleared from the body, and the result is typically harmless in healthy people. This can occur after manipulation of parts of the body normally colonized by bacteria, such as the mucosal surfaces of the mouth during teeth brushing, flossing, or dental procedures, or instrumentation of the bladder or colon. Intermittent bacteremia is characterized by periodic seeding of the same bacteria into the bloodstream by an existing infection elsewhere in the body, such as an abscess, pneumonia, or bone infection, followed by clearing of that bacteria from the bloodstream. This cycle will often repeat until the existing infection is successfully treated. Persistent bacteremia is characterized by the continuous presence of bacteria in the bloodstream. It is usually the result of an infected heart valve, a central line-associated bloodstream infection (CLABSI), an infected blood clot (suppurative thrombophlebitis), or an infected blood vessel graft. Persistent bacteremia can also occur as part of the infection process of typhoid fever, brucellosis, and bacterial meningitis. Left untreated, conditions causing persistent bacteremia can be potentially fatal.
Bacteremia is clinically distinct from sepsis, which is a condition where the blood stream infection is associated with an inflammatory response from the body, often causing abnormalities in body temperature, heart rate, breathing rate, blood pressure, and white blood cell count.
Bacteremia frequently evokes a response from the immune system called Sepsis, which consists of symptoms such as fever, chills, and hypotension. Severe immune responses to bacteremia may result in septic shock and multiple organ dysfunction syndrome, which are potentially fatal.
Bacteremia can travel through the blood stream to distant sites in the body and cause infection (hematogenous spread). Hematogenous spread of bacteria is part of the pathophysiology of certain infections of the heart (endocarditis), structures around the brain (meningitis), and tuberculosis of the spine (Pott's disease). Hematogenous spread of bacteria is responsible for many bone infections (osteomyelitis).
Prior to widespread use of vaccines, occult bacteremia was an important consideration in febrile children that appeared otherwise well.
Bacteria can enter the bloodstream in a number of different ways. However, for each major classification of bacteria (gram negative, gram positive, or anaerobic) there are characteristic sources or routes of entry into the bloodstream that lead to bacteremia. Causes of bacteremia can additionally be divided into healthcare-associated (acquired during the process of receiving care in a healthcare facility) or community-acquired (acquired outside of a health facility, often prior to hospitalization).
Gram positive bacteremia
Gram positive bacteria are an increasingly important cause of bacteremia. Staphyloccocus, streptococcus, and enterococcus species are the most important and most common species of gram-positive bacteria that can enter the bloodstream. These bacteria are normally found on the skin or in the gastrointestinal tract.
Staphylococcus aureus is the most common cause of healthcare-associated bacteremia in North and South America and is also an important cause of community-acquired bacteremia. Skin ulceration or wounds, respiratory tract infections, and IV drug use are the most important causes of community-acquired staph aureus bacteremia. In healthcare settings, intravenous catheters, urinary tract catheters, and surgical procedures are the most common causes of staph aureus bacteremia.
There are many different types of streptococcal species that can cause bacteremia. Group A streptococcus (GAS) typically causes bacteremia from skin and soft tissue infections. Group B streptococcus is an important cause of bacteremia in neonates, often immediately following birth. Viridans streptococci species are normal bacterial flora of the mouth. Viridans strep can cause temporary bacteremia after eating, toothbrushing, or flossing. More severe bacteremia can occur following dental procedures or in patients receiving chemotherapy. Finally, streptococcus bovis is a common cause of bacteremia in patients with colon cancer.
Enterococci are an important cause of healthcare-associated bacteremia. These bacteria commonly live in the gastrointestinal tract and female genital tract. Intravenous catheters, urinary tract infections and surgical wounds are all risk factors for developing bacteremia from enterococcal species. Resistant enterococcal species can cause bacteremia in patients who have had long hospital stays or frequent antibiotic use in the past.
Gram negative bacteremia
Gram negative bacterial species are responsible for approximately 24% of all cases of healthcare-associated bacteremia and 45% of all cases of community-acquired bacteremia. In general, gram negative bacteria enter the bloodstream from infections in the respiratory tract, genitourinary tract, gastrointestinal tract, or hepatobiliary system. Gram-negative bacteremia occurs more frequently in elderly populations (65 years or older) and is associated with higher morbidity and mortality in this population.
E.coli is the most common cause of community-acquired bacteremia accounting for approximately 75% of cases. E.coli bacteremia is usually the result of a urinary tract infection. Other organisms that can cause community-acquired bacteremia include Pseudomonas aeruginosa, Klebsiella pneumoniae, and Proteus mirabilis. Salmonella infection, despite mainly only resulting in gastroenteritis in the developed world, is a common cause of bacteremia in Africa. It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages.
Among healthcare-associated cases of bacteremia, gram negative organisms are an important cause of bacteremia in the ICU. Catheters in the veins, arteries, or urinary tract can all create a way for gram negative bacteria to enter the bloodstream. Surgical procedures of the genitourinary tract, intestinal tract, or hepatobiliary tract can also lead to gram negative bacteremia. Pseudomonas and Enterobacter species are the most important causes of gram negative bacteremia in the ICU.
Bacteremia risk factors
- HIV infection
- Diabetes Mellitus
- Chronic hemodialysis
- Solid organ transplant
- Stem cell transplant
- Treatment with glucocorticoids
- Liver failure
Bacteremia is most commonly diagnosed by blood culture, in which a sample of blood drawn from the vein by needle puncture is allowed to incubate with a medium that promotes bacterial growth. If bacteria are present in the bloodstream at the time the sample is obtained, the bacteria will multiply and can thereby be detected.
Any bacteria that incidentally find their way to the culture medium will also multiply. For example, if the skin is not adequately cleaned before needle puncture, contamination of the blood sample with normal bacteria that live on the surface of the skin can occur. For this reason, blood cultures must be drawn with great attention to sterile process. The presence of certain bacteria in the blood culture, such as Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli almost never represent a contamination of the sample. On the other hand, contamination may be more highly suspected if organisms like Staphylococcus epidermidis or Propionibacterium acnes grow in the blood culture.
Two blood cultures drawn from separate sites of the body are often sufficient to diagnose bacteremia. Two out of two cultures growing the same type of bacteria usually represents a real bacteremia, particularly if the organism that grows is not a common contaminant. One out of two positive cultures will usually prompt a repeat set of blood cultures to be drawn to confirm whether a contaminant or a real bacteremia is present. The patient's skin is typically cleaned with an alcohol-based product prior to drawing blood to prevent contamination. Blood cultures may be repeated at intervals to determine if persistent — rather than transient — bacteremia is present.
Prior to drawing blood cultures, a thorough patient history should be taken with particular regard to presence of both fevers and chills, other focal signs of infection such as in the skin or soft tissue, a state of immunosuppression, or any recent invasive procedures.
The treatment of bacteremia should begin with empiric antibiotic coverage. Any patient presenting with signs or symptoms of bacteremia or a positive blood culture should be started on intravenous antibiotics. The choice of antibiotic is determined by the most likely source of infection and by the characteristic organisms that typically cause that infection. Other important considerations include the patient's past history of antibiotic use, the severity of the presenting symptoms, and any allergies to antibiotics. Empiric antibiotics should be narrowed, preferably to a single antibiotic, once the blood culture returns with a particular bacteria that has been isolated.
Gram positive bacteremia
The Infectious Disease Society of America (IDSA) recommends treating uncomplicated methicillin resistant staph aureus (MRSA) bacteremia with a 14-day course of intravenous vancomycin. Uncomplicated bacteremia is defined as having positive blood cultures for MRSA, but having no evidence of endocarditis, no implanted prostheses, negative blood cultures after 2–4 days of treatment, and signs of clinical improvement after 72 hrs.
The antibiotic treatment of choice for streptococcal and enteroccal infections differs by species. However, it is important to look at the antibiotic resistance pattern for each species from the blood culture to better treat infections caused by resistant organisms.
Gram negative bacteremia
The treatment of gram negative bacteremia is also highly dependent on the causative organism. Empiric antibiotic therapy should be guided by the most likely source of infection and the patient's past exposure to healthcare facilities. In particular, a recent history of exposure to a healthcare setting may necessitate the need for antibiotics with pseudomonas aeruginosa coverage or broader coverage for resistant organisms. Extended generation cephalosporins such as ceftriaxone or beta lactam/beta lactam inhibitor antibiotics such as piperacillin-tazobactam are frequently used for the treatment of gram negative bacteremia.
For healthcare-associated bacteremia due to intravenous catheters, the IDSA has published guidelines for catheter removal. Short term catheters (in place <14 days) should be removed if bacteremia is caused by any gram negative bacteria, staph aureus, enterococci or mycobacteria. Long term catheters (>14 days) should be removed if the patient is developing signs or symptoms of sepsis or endocarditis, or if blood cultures remain positive for more than 72 hours.
- Ochei; et al. "Pus Abscess and Wound Drain". Medical Laboratory Science : Theory And Practice. Tata McGraw-Hill Education, 2000. p. 622.
- Doern, Gary (September 13, 2016). "Blood Cultures for the Detection of Bacteremia". uptodate.com. uptodate.com. Retrieved December 1, 2016.
- Fan, Shu-Ling; Miller, Nancy S.; Lee, John; Remick, Daniel G. (2016-09-01). "Diagnosing sepsis - The role of laboratory medicine". Clinica Chimica Acta; International Journal of Clinical Chemistry. 460: 203–210. doi:10.1016/j.cca.2016.07.002. ISSN 1873-3492. PMC 4980259. PMID 27387712.
- Sligl, Wendy; Taylor, Geoffrey; Brindley, Peter G. (2006-07-01). "Five years of nosocomial Gram-negative bacteremia in a general intensive care unit: epidemiology, antimicrobial susceptibility patterns, and outcomes". International Journal of Infectious Diseases. 10 (4): 320–325. doi:10.1016/j.ijid.2005.07.003. ISSN 1201-9712. PMID 16460982.
- Perez-Chaparro, P. J.; Meuric, V.; De Mello, G.; Bonnaure-Mallet, M. (2011-11-01). "[Bacteremia of oral origin]". Revue de Stomatologie et de Chirurgie Maxillo-Faciale. 112 (5): 300–303. doi:10.1016/j.stomax.2011.08.012. ISSN 1776-257X. PMID 21940028.
- Singer, Mervyn; Deutschman, Clifford S.; Seymour, Christopher Warren; Shankar-Hari, Manu; Annane, Djillali; Bauer, Michael; Bellomo, Rinaldo; Bernard, Gordon R.; Chiche, Jean-Daniel (2016-02-23). "The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3)". JAMA. 315 (8): 801–810. doi:10.1001/jama.2016.0287. ISSN 1538-3598. PMC 4968574. PMID 26903338.
- Zeman, Florian; Koller, Michael; Schecklmann, Martin; Langguth, Berthold; Landgrebe, Michael (2012-10-18). "Tinnitus assessment by means of standardized self-report questionnaires: Psychometric properties of the Tinnitus Questionnaire (TQ), the Tinnitus Handicap Inventory (THI), and their short versions in an international and multi-lingual sample". Health and Quality of Life Outcomes. 10: 128. doi:10.1186/1477-7525-10-128. ISSN 1477-7525. PMC 3541124. PMID 23078754.
- Yang, Lu; Tang, Zhuang; Gao, Liang; Li, Tao; Chen, Yongji; Liu, Liangren; Han, Ping; Li, Xiang; Dong, Qiang (2016-08-01). "The augmented prophylactic antibiotic could be more efficacious in patients undergoing transrectal prostate biopsy: a systematic review and meta-analysis". International Urology and Nephrology. 48 (8): 1197–1207. doi:10.1007/s11255-016-1299-7. ISSN 1573-2584. PMID 27160220.
- Seifert, Harald (2009-05-15). "The Clinical Importance of Microbiological Findings in the Diagnosis and Management of Bloodstream Infections". Clinical Infectious Diseases. 48 (Supplement 4): S238–S245. doi:10.1086/598188. ISSN 1058-4838. PMID 19374579.
- "IDP200 Pathophysiology of Infectious Diseases, Fall 2004/2005 - Tufts OpenCourseWare". ocw.tufts.edu. Retrieved 2016-12-07.
- "IDP200 Pathophysiology of Infectious Diseases, Fall 2004/2005 - Tufts OpenCourseWare". ocw.tufts.edu. Retrieved 2016-12-07.
- Medical Microbiology, 27e. New York: McGraw-Hill Education. 2016. pp. Chapter 9. ISBN 9780-0-71-82498-9 – via http://accessmedicine.mhmedical.com/content.aspx?bookid=1551&Sectionid=94106209.
- Sherris Medical Microbiology, 6e. New York: McGraw-Hill. 2014. pp. Infectious Diseases: Syndromes and Etiologies. ISBN 9780-0-7-181821-6 – via http://accessmedicine.mhmedical.com/content.aspx?bookid=1020&Sectionid=56968846.
- Cohen-Poradosu, Ronit (2015). Harrison's Principles of Internal Medicine, 19e. New York: McGraw-Hill. pp. Chapter 201. ISBN 978-0-07-180215-4 – via http://accessmedicine.mhmedical.com/content.aspx?bookid=1130&Sectionid=79736907.
- Forner, Lone; Larsen, Tove; Kilian, Mogens; Holmstrup, Palle (2006-06-01). "Incidence of bacteremia after chewing, tooth brushing and scaling in individuals with periodontal inflammation". Journal of Clinical Periodontology. 33 (6): 401–407. doi:10.1111/j.1600-051X.2006.00924.x. ISSN 1600-051X. PMID 16677328.
- Cohen-Poradosu, Ronit (2015). Harrison's Principles of Internal Medicine 19th Edition. New York: McGraw Hill. pp. Chapter 201. ISBN 978-0-07-180215-4.
- Kaplan, MD, Lewis (2016-08-16). "Systemic Inflammatory Response Syndrome: Background, Pathophysiology, Etiology". Medscape.
- Scott, Michael C. (2017-02-01). "Defining and Diagnosing Sepsis". Emergency Medicine Clinics of North America. 35 (1): 1–9. doi:10.1016/j.emc.2016.08.002. ISSN 1558-0539. PMID 27908326.
- Agarwal, Anil; Aggarwal, Aditya N. (2016-08-01). "Bone and Joint Infections in Children: Acute Hematogenous Osteomyelitis". Indian Journal of Pediatrics. 83 (8): 817–824. doi:10.1007/s12098-015-1806-3. ISSN 0973-7693. PMID 26096866.
- Guay, David R. (2012-02-01). "Antimicrobial prophylaxis in noncardiac prosthetic device recipients". Hospital Practice (1995). 40 (1): 44–74. doi:10.3810/hp.2012.02.947. ISSN 2154-8331. PMID 22406882.
- "Fever without a source in children 3 to 36 months of age".
- Cervera, Carlos; Almela, Manel; Martínez-Martínez, José A.; Moreno, Asunción; Miró, José M. (2009-01-01). "Risk factors and management of Gram-positive bacteraemia". International Journal of Antimicrobial Agents. 34 Suppl 4: S26–30. doi:10.1016/S0924-8579(09)70562-X. ISSN 1872-7913. PMID 19931813.
- Biedenbach, Douglas J.; Moet, Gary J.; Jones, Ronald N. (2004-09-01). "Occurrence and antimicrobial resistance pattern comparisons among bloodstream infection isolates from the SENTRY Antimicrobial Surveillance Program (1997-2002)". Diagnostic Microbiology and Infectious Disease. 50 (1): 59–69. doi:10.1016/j.diagmicrobio.2004.05.003. ISSN 0732-8893. PMID 15380279.
- Lowy, Franklin D. (1998-08-20). "Staphylococcus aureus Infections". New England Journal of Medicine. 339 (8): 520–532. doi:10.1056/NEJM199808203390806. ISSN 0028-4793. PMID 9709046.
- Schwartz, Brian (2016). Current Medical Diagnosis and Treatment 2017. New York: McGraw Hill. pp. Chapter 33. ISBN 978-1-25-958511-1.
- Mayer, Robert (2015). Harrison's Principles of Internal Medicine 19th Edition. New York: McGraw Hill. pp. Chapter 110. ISBN 978-0-07-180215-4.
- Arias, Cesar (2015). Harrison's Principles of Internal Medicine 19th Edition. New York: McGraw Hill. pp. Chapter 174. ISBN 978-0-07-180215-4.
- Kasper, Dennis (2015). Harrison's Manual of Medicine. New York: McGraw Hill. pp. Chapter 87. ISBN 978-0-07-182852-9.
- Gaynes, Robert; Edwards, Jonathan R.; National Nosocomial Infections Surveillance System (2005-09-15). "Overview of nosocomial infections caused by gram-negative bacilli". Clinical Infectious Diseases. 41 (6): 848–854. doi:10.1086/432803. ISSN 1537-6591. PMID 16107985.
- Diekema, D. J.; Beekmann, S. E.; Chapin, K. C.; Morel, K. A.; Munson, E.; Doern, G. V. (2003-08-01). "Epidemiology and outcome of nosocomial and community-onset bloodstream infection". Journal of Clinical Microbiology. 41 (8): 3655–3660. doi:10.1128/JCM.41.8.3655-3660.2003. ISSN 0095-1137. PMC 179863. PMID 12904371.
- High, Kevin (2017). Geriatric Medicine and Gerontology 7th Edition. New York: McGraw Hill. pp. Chapter 125. ISBN 978-0-07-183345-5.
- Luzzaro, F.; Viganò, E. F.; Fossati, D.; Grossi, A.; Sala, A.; Sturla, C.; Saudelli, M.; Toniolo, A.; AMCLI Lombardia Hospital Infectious Study Group (2002-12-01). "Prevalence and drug susceptibility of pathogens causing bloodstream infections in northern Italy: a two-year study in 16 hospitals". European Journal of Clinical Microbiology & Infectious Diseases. 21 (12): 849–855. doi:10.1007/s10096-002-0837-7. ISSN 0934-9723. PMID 12525919.
- Deen, Jacqueline; von Seidlein, Lorenz; Andersen, Finn; Elle, Nelson; White, Nicholas J.; Lubell, Yoel (2012-06-01). "Community-acquired bacterial bloodstream infections in developing countries in south and southeast Asia: a systematic review". The Lancet. Infectious Diseases. 12 (6): 480–487. doi:10.1016/S1473-3099(12)70028-2. ISSN 1474-4457. PMID 22632186.
- Peleg, Anton Y.; Hooper, David C. (2010-05-13). "Hospital-Acquired Infections Due to Gram-Negative Bacteria". The New England Journal of Medicine. 362 (19): 1804–1813. doi:10.1056/NEJMra0904124. ISSN 0028-4793. PMC 3107499. PMID 20463340.
- Graff, Larissa R.; Franklin, Kristal K.; Witt, Lana; Cohen, Neal; Jacobs, Richard A.; Tompkins, Lucy; Guglielmo, B. Joseph (2002-02-15). "Antimicrobial therapy of gram-negative bacteremia at two university-affiliated medical centers". The American Journal of Medicine. 112 (3): 204–211. doi:10.1016/s0002-9343(01)01092-0. ISSN 0002-9343. PMID 11893347.
- Brigden, M. L. (2001-02-01). "Detection, education and management of the asplenic or hyposplenic patient". American Family Physician. 63 (3): 499–506, 508. ISSN 0002-838X. PMID 11272299.
- Coburn, Bryan; Morris, Andrew M.; Tomlinson, George; Detsky, Allan S. (2012-08-01). "Does This Adult Patient With Suspected Bacteremia Require Blood Cultures?". JAMA. 308 (5): 502. doi:10.1001/jama.2012.8262. ISSN 0098-7484.
- Hall, Keri K.; Lyman, Jason A. (2016-12-16). "Updated Review of Blood Culture Contamination". Clinical Microbiology Reviews. 19 (4): 788–802. doi:10.1128/CMR.00062-05. ISSN 0893-8512. PMC 1592696. PMID 17041144.
- Holland, TL; Arnold, C; Fowler VG, Jr (1 October 2014). "Clinical management of Staphylococcus aureus bacteremia: a review". JAMA. 312 (13): 1330–41. doi:10.1001/jama.2014.9743. PMC 4263314. PMID 25268440.
- Hooper, David (2016). Harrison's Principles of Internal Medicine 19th Edition. New York: McGraw Hill. pp. Chapter 170. ISBN 978-0-07-180215-4.
- Liu, Catherine; Bayer, Arnold; Cosgrove, Sara E.; Daum, Robert S.; Fridkin, Scott K.; Gorwitz, Rachel J.; Kaplan, Sheldon L.; Karchmer, Adolf W.; Levine, Donald P. (2011-02-01). "Clinical practice guidelines by the infectious diseases society of america for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children". Clinical Infectious Diseases. 52 (3): e18–55. doi:10.1093/cid/ciq146. ISSN 1537-6591. PMID 21208910.
- Russo, Thomas (2016). Harrison's Principles of Internal Medicine 19th Edition. New York: McGraw Hill. pp. Chapter 186. ISBN 978-0-07-180215-4.
- Mermel, Leonard A.; Allon, Michael; Bouza, Emilio; Craven, Donald E.; Flynn, Patricia; O'Grady, Naomi P.; Raad, Issam I.; Rijnders, Bart J. A.; Sherertz, Robert J. (2009-07-01). "Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 Update by the Infectious Diseases Society of America". Clinical Infectious Diseases. 49 (1): 1–45. doi:10.1086/599376. ISSN 1537-6591. PMC 4039170. PMID 19489710.