Chlamydia pneumoniae [TWAR strain] in respiratory tract infections: a comparative study between different methods for its isolation

ABSTRACT

Chlamydia pneumoniae [C. peumoniae], is a common pathogen found in the respiratory tract, it has a seroprevalence rate of > 70% in the adult population, and it is considered responsible for about 10% of the cases of community-acquired pneumonia. Owing to the difficulties in the laboratory diagnosis of C. pneumoniae infection, a routine diagnostic service for this pathogen is not currently available. Moreover, diagnostic differences between the various techniques are not fully resolved. The present study was conducted to evaluate the utility of Direct Fluorescent Antibody [DFA], Tissue Culture [TC], PCR and microimmunofluorescence [MIF] assays for the diagnosis of C. pneumoniae infection in patients having respiratory symptoms. A total of 45 throat and retropharyngeal swabs as well as broncho-alveolar lavage specimens -collected from patients suffering from respiratory tract infections [RTIs]- were tested for the presence of C. pneumoniae by Direct Fluorescent Antibody staining [DFA, Bio Merieux], tissue culture on Hep-2 cell monolayer [Vacsera], PCR using species specific primer pair HR-1/MH-1 [Dia-sorin], and their sera were tested for the presence of IgG antibodies against C. pneumoniae by microimmunofluorescence assays [Vircell, S.L]. PCR gave the highest positive detection rate [44.4%], followed by DFA [28.8%], then TC [22.2%], while MIF gave the least [15.5%]. According to the clinical conditions; acute exacerbation of bronchial asthma, acute bronchitis, pneumonia and asthmatic bronchitis gave positive results with DFA, TC and PCR. Acute exacerbation of chronic obstructive pulmonary disease [COPD] gave positive results with DFA and PCR. PCR is the only assay that gave positive results with chronic bronchitis. In conclusion the difference between the various techniques applied for the diagnosis of C. pneumoniae infection is not fully resolved and it is difficult to define a perfect gold standard