Acute infection Chlamydia pneumoniae is a common cause of pneumonia around the world; it is typically acquired by otherwise-healthy people and is a form of
community-acquired pneumonia. Its treatment and diagnosis are different from historically recognized causes, such as
Streptococcus pneumoniae. Because it does not gram stain well, and because
C. pneumoniae bacteria 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 by
C. pneumoniae is categorized as an "
atypical pneumonia".
Chlamydia pneumoniae infection was first associated with wheezing, asthmatic bronchitis, and adult-onset
asthma in 1991. 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 of
C. pneumoniae by direct organism identification.
C. pneumoniae infection triggers acute wheezing, if it becomes chronic then it is diagnosed as asthma. These observations suggest that acute
C. pneumoniae infection is capable of causing protean manifestations of chronic respiratory illness which lead to asthma. 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 and two randomized controlled trials of azithromycin treatment for asthma. One of these RCTs suggest that the treatment effect may be greatest in patients with severe, refractory asthma. These clinical results correlate with epidemiological evidence that
C. pneumoniae is positively associated with asthma severity and laboratory evidence that
C. pneumoniae infection creates steroid-resistance. 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. More recent positive results of long-term treatment with azithromycin on asthma exacerbations and quality-of-life in patients with severe, refractory asthma have resulted in azithromycin now being recommended in international guidelines as a treatment option for these types of patients. 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). Randomized, controlled trials that include these types of asthma patients are needed.
Chronic diseases Chronic
C. pneumoniae infection has been documented via direct organism detection ( and/or
culture) in
sputum and
bronchoalveolar lavage (BAL) of children with chronic respiratory conditions including asthma, and in peripheral blood of healthy blood donors.
C. pneumoniae has also been detected by
immunohistochemical staining in the
monocytes residing within the lungs of 100% of patients undergoing lung resection for cancer; patients with comorbid COPD had significantly higher infection burden than those without COPD. The same study found that 44% of young and middle aged accident victims were also chronically infected, albeit with significantly lower infection burden. One
meta-analysis of
serological data comparing prior
C. pneumoniae infection in patients with and without lung cancer found results suggesting prior infection was associated with an increased risk of developing lung cancer. In research into the association between
C. pneumoniae infection and
atherosclerosis and
coronary artery disease,
serological testing, direct pathologic analysis of plaques, and
in vitro testing suggest infection with
C. pneumoniae is a significant risk factor for development of atherosclerotic
plaques and atherosclerosis.
C. pneumoniae infection increases adherence of
macrophages to
endothelial cells in vitro and aortas
ex vivo. However, most current research and data are insufficient and do not define how often
C. pneumoniae is found in atherosclerotic or normal
vascular tissue.
Chlamydia pneumoniae has also been found in the cerebrospinal fluid of patients diagnosed with multiple sclerosis.
Chlamydia pneumoniae infection has been associated with
schizophrenia. Many other pathogens have been associated with schizophrenia as well. ==Treatment==