Wikipedia

Chlamydia pneumoniae

Chlamydia pneumoniae[1]is a species ofChlamydia,anobligate intracellularbacterium[2]that infects humans and is a major cause ofpneumonia.It was known as the Taiwan acute respiratory agent (TWAR) from the names of the two original isolates – Taiwan (TW-183) and an acute respiratory isolate designated AR-39.[3]Briefly, it was known asChlamydophila pneumoniae,and that name is used as an alternate in some sources.[4]In some cases, to avoid confusion, both names are given.[5]

Chlamydia pneumoniae
Scientific classificationEdit this classification
Domain: Bacteria
Phylum: Chlamydiota
Class: Chlamydiia
Order: Chlamydiales
Family: Chlamydiaceae
Genus: Chlamydia
Species:
C. pneumoniae
Binomial name
Chlamydia pneumoniae
Graystonet al.1989
Synonyms
  • Chlamydophila pneumoniae(Grayston et al. 1989) Everett, Bush & Andersen 1999

Chlamydia pneumoniaehas a complex life cycle and must infect another cell toreproduce;thus, it is classified as anobligate intracellular pathogen.The fullgenomesequence forC. pneumoniaewas published in 1999.[6]It also infects and causes disease inkoalas,emerald tree boas(Corallus caninus),iguanas,chameleons,frogs, and turtles.

The first known case of infection withC. pneumoniaewas a case ofconjunctivitisinTaiwanin 1950. There are no known cases ofC. pneumoniaein human history before 1950. This atypical bacterium commonly causespharyngitis,bronchitis,coronary artery diseaseandatypical pneumoniain addition to several other possible diseases.[7][8]

Micrograph ofChlamydia pneumoniaein an epithelial cell in acute bronchitis: 1 – infected epitheliocyte, 2 – uninfected epitheliocytes, 3 – chlamydial inclusion bodies in cell, 4 – cell nuclei

Life cycle and method of infection

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Life cycle ofChlamydia pneumoniae.A —Chlamydiaelementary body. B — Lung cell. 2 —Chlamydiaenters the cell. 3—Elementary body becomes a reticulate body. 4 — Replication. 5 — Reticulate bodies become elementary bodies and are released to infect other cells.[citation needed]

Chlamydia pneumoniaeis a small gram-negative bacterium (0.2 to 1μm) that undergoes several transformations during its life cycle. It exists as anelementary body(EB) betweenhosts.The EB is not biologically active, but is resistant toenvironmentalstresses and can survive outside a host for a limited time. The EB travels from aninfectedperson to thelungsof an uninfected person in smalldropletsand is responsible for infection. Once in the lungs, the EB is taken up bycellsin a pouch called anendosomeby a process calledphagocytosis.However, the EB is not destroyed by fusion withlysosomes,as is typical for phagocytosed material. Instead, it transforms into areticulate body(RB) and begins to replicate within the endosome. The reticulate bodies must use some of the host's cellular metabolism 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 sameorganismor in a new host. Thus, the lifecycle ofC. pneumoniaeis divided between the elementary body, which is able to infect new hosts but cannot replicate, and the reticulate body, which replicates but is not able to cause a new infection.[9]

Diseases

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See also:Asthma-related microbes

Chlamydia pneumoniaeis a common cause of pneumonia around the world; it is typically acquired by otherwise-healthy people and is a form ofcommunity-acquired pneumonia.Its treatment and diagnosis are different from historically recognized causes, such asStreptococcus pneumoniae.[10]Because it does not gram stain well, and becauseC. pneumoniaebacteria is very different from the many other bacteria causing pneumonia (in the earlier days, it was even thought to be a virus), the pneumonia caused byC. pneumoniaeis categorized as an "atypical pneumonia".[11]

Onemeta-analysisofserologicaldata comparing priorC. pneumoniaeinfection in patients with and without lung cancer found results suggesting prior infection was associated with an increased risk of developing lung cancer.[12][13][14]

In research into the association betweenC. pneumoniaeinfection andatherosclerosisandcoronary artery disease,serologicaltesting, direct pathologic analysis of plaques, andin vitrotesting suggest infection withC. pneumoniaeis a significant risk factor for development of atheroscleroticplaquesand atherosclerosis.[15]C. pneumoniaeinfection increases adherence ofmacrophagestoendothelial cellsin vitroand aortasex vivo.[16]However, most current research and data are insufficient and do not define how oftenC. pneumoniaeis found in atherosclerotic or normalvasculartissue.[17]

Chlamydia pneumoniaehas also been found in the cerebrospinal fluid of patients diagnosed with multiple sclerosis.[18]

Chlamydia pneumoniaeinfection was first associated with wheezing, asthmatic bronchitis, and adult-onset asthma in 1991.[19]Subsequent studies of bronchoalveolar lavage fluid from pediatric patients with asthma and also other severe chronic respiratory illnesses have demonstrated that over 50 percent had evidence ofC. pneumoniaeby direct organism identification.[20][21]C. pneumoniaeinfection triggers acute wheezing, if it becomes chronic then it is diagnosed as asthma.[22]These observations suggest that acuteC. pneumoniaeinfection is capable of causing protean manifestations of chronic respiratory illness which lead to asthma.[23]

Macrolide antibiotic treatment can improve asthma in a subgroup of patients that remains to be clearly defined. Macrolide benefits were first suggested in two observational trials[24][25]and two randomized controlled trials[26][27]of azithromycin treatment for asthma. One of these RCTs[27]and another macrolide trial[28]suggest that the treatment effect may be greatest in patients with severe, refractory asthma. These clinical results correlate with epidemiological evidence thatC. pneumoniaeis positively associated with asthma severity[29]and laboratory evidence thatC. pneumoniaeinfection creates steroid-resistance.[30]A meta analysis of 12 RCTs of macrolides for the long term management of asthma found significant effects on asthma symptoms, quality of life, bronchial hyper reactivity and peak flow but not FEV1.[31]More recent positive results of long-term treatment with azithromycin on asthma exacerbations and quality-of-life in patients with severe, refractory asthma[32][33]have resulted in azithromycin now being recommended in international guidelines as a treatment option for these types of patients.[34]

A recent case series of 101 adults with asthma reported that macrolides (mostly azithromycin) and tetracyclines, either separately or in combination, appeared to be dramatically efficacious in a subgroup of "difficult-to-treat" (i.e., not necessarily refractory to high-dose inhaled corticosteroids but who did not take them) patients with severe asthma, many of whom also had the "overlap syndrome" (asthma and COPD).[35]Randomized, controlled trials that include these types of asthma patients are needed.

Chlamydia pneumoniaeinfection has been associated withschizophrenia.[36]Many other pathogens have been associated with schizophrenia as well.[36]ChronicChlamydia pneumoniaeinfection has also in some cases been found to be a cause ofchronic fatigue syndrome(CFS) that can be resolved with antibiotics.[37][38]

Treatment

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Thefirst-lineantibioticsfor treatment ofChlamydia pneumoniaeare themacrolideerythromycinand thetetracyclinestetracyclineanddoxycycline.[39]The macrolidesclarithromycinandazithromycinare also effective.[39]Chlamydia pneumoniaeshows resistance topenicillin,ampicillin,andsulfa drugs,and hence these antibiotics are not recommended.[39]Other antibiotics which may be effective includefluoroquinoloneslikelevofloxacin,gatifloxacin,gemifloxacin,andmoxifloxacin.[39]Symptoms ofChlamydia pneumoniaeoften reappear after short or conventional courses of antibiotics.[39]As a result, following confirmation of persistent infection with culture, intensive long-term treatment is recommended.[39]

Vaccine research

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There is currently no vaccine to protect againstChlamydia pneumoniae.Identification of immunogenicantigensis critical for the construction of an efficacious subunit vaccine againstC. pneumoniaeinfections. Additionally, there is a general shortage worldwide of facilities that can identify/diagnoseChlamydia pneumoniae.[citation needed]

References

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  1. ^Everett KD, Bush RM, Andersen AA (April 1999)."Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms".International Journal of Systematic Bacteriology.49(2):415–40.doi:10.1099/00207713-49-2-415.PMID10319462.
  2. ^Chlamydia+pneumoniaeat the U.S. National Library of MedicineMedical Subject Headings(MeSH)
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  22. ^Hahn DL, McDonald R (October 1998). "Can acute Chlamydia pneumoniae respiratory tract infection initiate chronic asthma?".Annals of Allergy, Asthma & Immunology.81(4):339–44.doi:10.1016/S1081-1206(10)63126-2.PMID9809498.
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  28. ^Simpson JL, Powell H, Boyle MJ, Scott RJ, Gibson PG (January 2008). "Clarithromycin targets neutrophilic airway inflammation in refractory asthma".American Journal of Respiratory and Critical Care Medicine.177(2):148–55.CiteSeerX10.1.1.318.5663.doi:10.1164/rccm.200707-1134OC.PMID17947611.
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  31. ^Reiter J, Demirel N, Mendy A, Gasana J, Vieira ER, Colin AA, Quizon A, Forno E (August 2013). "Macrolides for the long-term management of asthma--a meta-analysis of randomized clinical trials".Allergy.68(8):1040–9.doi:10.1111/all.12199.PMID23895667.S2CID17057866.
  32. ^Gibson, PG (2017). "Effect of azithromycin on asthma exacerbations and quality of life in adults with persistent uncontrolled asthma (AMAZES): a randomised, double-blind, placebo-controlled trial".Lancet.390(10095):659–668.doi:10.1016/S0140-6736(17)31281-3.PMID28687413.S2CID4523731.
  33. ^Gibson, PG (2019)."Efficacy of azithromycin in severe asthma from the AMAZES randomised trial".ERJ Open Res.5(4):00056–2019.doi:10.1183/23120541.00056-2019.PMC6926362.PMID31886156.
  34. ^GINA."Difficult-to-Treat and Severe Asthma in Adolescent and Adult Patients: Diagnosis and Management".Global Initiative for Asthma.RetrievedAugust 1,2021.
  35. ^Wagshul, FA (2021)."Outcomes of Antibiotics in Adults with" Difficult to Treat "Asthma or the Overlap Syndrome".J Asthma Allergy.14:703–712.doi:10.2147/JAA.S313480.PMC8216074.PMID34163182.
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  38. ^Chia JK, Chia LY (August 1999). "Chronic Chlamydia pneumoniae infection: a treatable cause of chronic fatigue syndrome".Clin Infect Dis.29(2):452–453.doi:10.1086/520239.PMID10476765.
  39. ^abcdefBurillo A, Bouza E (March 2010). "Chlamydophila pneumoniae".Infect Dis Clin North Am.24(1):61–71.doi:10.1016/j.idc.2009.10.002.PMID20171546.
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