Chlamydia pneumoniae
| Chlamydia pneumoniae | |
|---|---|
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Order: | |
| Family: | |
| Genus: | |
| Species: | C. pneumoniae
|
Chlamydophila pneumoniae is a species of Chlamydophila bacteria[1][2][3] that infects humans and is a major cause of pneumonia.
Until recently it was known as "Chlamydia pneumoniae", and that name is used as an alternate in some sources.[4] In some cases, to avoid confusion, both names are given.[5]
C. pneumoniae has a complex life cycle and must infect another cell in order to reproduce and thus is classified as an obligate intracellular pathogen. In addition to its role in pneumonia, there is evidence associating C. pneumoniae with atherosclerosis, Alzheimer's disease and with asthma. The full genome sequence for C. pneumoniae was published in 1999.
C. pneumoniae also infects and causes disease in Koalas, emerald tree boa (Corallus caninus), iguanas, chameleons, frogs, and turtles.
The first known case of infection with C. pneumoniae was a case of sinusitis in Taiwan.
This atypical bacterium commonly causes pharyngitis, bronchitis and atypical pneumonia[6] mainly in elderly and debilitated patients but in healthy adults also.[7]
Life cycle and method of infection
Chlamydia pneumoniae is a small bacterium (0.2 to 1 micrometer) that undergoes several transformations during its life cycle. It exists as an elementary body (EB) in between hosts. The EB is not biologically active but is resistant to environmental stresses and can survive outside of a host for a limited time. The EB travels from an infected person to the lungs of a non-infected person in small droplets and is responsible for infection. Once in the lungs, the EB is taken up by cells in a pouch called an endosome by a process called phagocytosis. However, the EB is not destroyed by fusion with lysosomes as is typical for phagocytosed material. Instead, it transforms into a reticulate body and begins to replicate within the endosome. The reticulate bodies must utilize some of the host's cellular machinery to complete its replication. The reticulate bodies then convert back to elementary bodies and are released back into the lung, often after causing the death of the host cell. The EBs are thereafter able to infect new cells, either in the same organism or in a new host. Thus, the life cycle of C. pneumoniae is divided between the elementary body which is able to infect new hosts but can not replicate and the reticulate body which replicates but is not able to cause new infection.
Pneumonia
C. pneumoniae is a common cause of pneumonia around the world. C. pneumoniae is typically acquired by otherwise healthy people and is a form of community-acquired pneumonia. Because treatment and diagnosis are different from historically recognized causes such as Streptococcus pneumoniae, pneumonia caused by C. pneumoniae is categorized as an "atypical pneumonia."
Symptoms and diagnosis
Symptoms of infection with C. pneumoniae are indistinguishable from other causes of pneumonia. These include cough, fever, and difficulties breathing. A slightly red hard palate, and a whitening of the back of the tongue are very common. Patients infected with C. pneumoniae often have nasal congestion, chest pressures and depression. C. pneumoniae more often causes pharyngitis, laryngitis, and sinusitis than other causes of pneumonia; however, because many other causes of pneumonia results in these symptoms, differentiation is not possible. Likewise, a physical examination by a health provider does not typically provide information which allows for a definite diagnosis.
Diagnosis of C. pneumoniae may be confounded by prior infections with this microorganism. Examination of sputum or the secretions of the respiratory tract may reveal signs of the bacteria. Otherwise, examination of the blood may reveal antibodies against the bacteria. Interpretation may require a period of six weeks in order to reanalyze the antibodies and to determine whether the infection was new or old. Examination of the blood may also show proteins (antigens) from C. pneumoniae, either through direct fluorescent antibody testing, enzyme-linked immunosorbent assay (ELISA), or polymerase chain reaction (PCR).
Chest x-rays of lungs infected with C. pneumoniae often show a small patch of increased shadow (opacity). However, many different patterns are common and there is no appearance which allows for a specific diagnosis.
Treatment and prognosis
Typically, treatment for pneumonia is begun before the causative microorganism is identified. This empiric therapy includes an antibiotic active against the atypical bacteria, including Chlamydia pneumoniae. The most common type of antibiotic used is a macrolide such as azithromycin or clarithromycin. If testing reveals that C. pneumoniae is the causative agent, therapy may be switched to doxycycline, which is slightly more effective against the bacteria. Sometimes a quinolone antibiotic such as levofloxacin may be started empirically. This group is not as effective against C. pneumoniae. Treatment is typically continued for ten to fourteen days for known infections. If the infection have prolonged during a long period of time (>6 months) it is typical that the treatment of the infection should be three weeks.
Prognosis of pneumonia caused by C. pneumoniae is excellent. Hospitalization is uncommon, complications are rare, and most people have no residual deficits. In fact, C. pneumoniae is a common cause of walking pneumonia, so named because most people are able to continue to walk and participate in reduced activity during infection.
Epidemiology and prevention
C. pneumoniae affects all age groups and is most common among the 60-79 year old and older teenage age group. Reinfection is common after a short period of immunity. The incidence is one case out of one thousand per year and causes ten percent of community-acquired pneumonias treated without hospitalization.[citation needed] As of 2009, there are no vaccines or other ways to prevent infection other than good hygiene.
Other illnesses
In addition to pneumonia, C. pneumoniae less commonly causes several other illnesses. Among these are meningoencephalitis (infection and inflammation of the brain and spinal cord), arthritis, myocarditis (inflammation of the heart), and Guillain-Barré syndrome (inflammation of the nerves). It has also been associated with dozens of other conditions, such as Alzheimer's disease, fibromyalgia, Chronic Fatigue Syndrome, prostatitis, and many others.
Links with chronic inflammatory diseases
 | This article needs additional citations for verification. (February 2007) |
In addition to acute infections already covered, C. pneumoniae has been implicated in several chronic diseases. Links between infection with C. pneumoniae heart attacks (myocardial infarction) and atherosclerosis have also been found.[8] In fact, C. pneumoniae has been found within plaques in the walls of coronary arteries supplying the heart.[9][10] Antibody levels against C. pneumoniae are also higher in people with heart problems.[11] As of 2009, short-term prescription of anti-chlamydial antibiotics has not been shown to decrease incidence of myocardial infarction.[12]
C. pneumoniae has also been found in the cerebrospinal fluid of some patients diagnosed with multiple sclerosis.[13]
References
- ^ Frikha-Gargouri O, Gdoura R, Znazen A; et al. (2008). "Evaluation and optimization of a commercial enzyme linked immunosorbent assay for detection of Chlamydophila pneumoniae IgA antibodies". BMC Infect. Dis. 8: 98. doi:10.1186/1471-2334-8-98. PMC 2515311. PMID 18655722.
{{cite journal}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ Cannon CP, Braunwald E, McCabe CH; et al. (2005). "Antibiotic treatment of Chlamydia pneumoniae after acute coronary syndrome". N. Engl. J. Med. 352 (16): 1646–54. doi:10.1056/NEJMoa043528. PMID 15843667.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Chlamydophila+pneumoniae at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- ^ "www.ncbi.nlm.nih.gov". Retrieved 2009-01-27.
- ^ Appelt DM, Roupas MR, Way DS; et al. (2008). "Inhibition of apoptosis in neuronal cells infected with Chlamydophila (Chlamydia) pneumoniae". BMC Neurosci. 9: 13. doi:10.1186/1471-2202-9-13. PMC 2266938. PMID 18218130.
{{cite journal}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ Lang, B. R., Chlamydia pneumonia as a differential diagnosis? Follow-up to a case report on progressive pneumonitis in an adolescent, Patient Care, Sept. 15, 1991
- ^ Little, Linda, Elusive pneumonia strain frustrates many clinicians, Medical Tribune, p. 6, September 19, 1991
- ^ Blasi F, Denti F, Erba M; et al. (1996). "Detection of Chlamydia pneumoniae but not Helicobacter pylori in atherosclerotic plaques of aortic aneurysms". J. Clin. Microbiol. 34 (11): 2766–9. PMC 229401. PMID 8897180.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Ramirez JA (1996). "Isolation of Chlamydia pneumoniae from the coronary artery of a patient with coronary atherosclerosis. The Chlamydia pneumoniae/Atherosclerosis Study Group". Ann. Intern. Med. 125 (12): 979–82. PMID 8967709.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Jackson LA, Campbell LA, Kuo CC, Rodriguez DI, Lee A, Grayston JT (1997). "Isolation of Chlamydia pneumoniae from a carotid endarterectomy specimen". J. Infect. Dis. 176 (1): 292–5. PMID 9207386.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Danesh J, Collins R, Peto R (1997). "Chronic infections and coronary heart disease: is there a link?". Lancet. 350 (9075): 430–6. doi:10.1016/S0140-6736(97)03079-1. PMID 9259669.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ M Stitzinger (2007). "Lipids, inflammation and atherosclerosis" (pdf). The digital repository of Leiden University. Retrieved 2007-11-02.
Results of clinical trials investigating anti-chlamydial antibiotics as an addition to standard therapy in patients with coronary artery disease have been inconsistent. Therefore, Andraws et al. conducted a meta- analysis of these clinical trials and found that evidence available to date does not demonstrate an overall benefit of antibiotic therapy in reducing mortality or cardiovascular events in patients with coronary artery disease.
- ^ Sriram S, Stratton CW, Yao S; et al. (1999). "Chlamydia pneumoniae infection of the central nervous system in multiple sclerosis". Ann. Neurol. 46 (1): 6–14. doi:10.1002/1531-8249(199907)46:1<6::AID-ANA4>3.0.CO;2-M. PMID 10401775.
{{cite journal}}: Explicit use of et al. in:|author=(help)CS1 maint: multiple names: authors list (link)