Identification of bacterial pathogens in patients with chronic obstructive pulmonary disease (COPD) with special reference to Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella pneumophila

Background Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality throughout the world. COPD is often accompanied by acute exacerbations [AECOPD] where 70% of it is caused by aerobic bacteria, 30% due to viruses and 5-10 % by atypical bacteria,most commonly Mycoplasma pneumoniae ( M. pneumoniae ), Chlamydia pneumoniae ( C. pneumoniae ) and Legionella pneumophila ( L.pneumophila ). Isolation and identification of these atypical microorganisms are challenging. However, the sensitivity in detecting these pathogens has improved with the availability of newer molecular diagnostic techniques. The present prospective study was undertaken to determine the predominant bacterial pathogens with special reference to atypical pathogens in patients with COPD using all three detection approaches in combination (serology, culture, PCR and RT-PCR). Methodology One hundred and ninety-six hospitalized patients, categorized into different stages of COPD and AECOPD using GOLD and Anthonisen criteria, were included in the study. Clinical samples such as throat swabs, nasopharyngeal swabs, sputum, urine and 10 ml of both acute and convalescent serum were collected. Isolation and identification of bacteria were done using standard methods. Atypical bacteria were identified by using phenotypic molecular methods. Antibody levels were detected in the serum using commercially available kits. Results Out of 196 patients, 39.8% patients were in the severe stage of COPD and 49.7% showed mild exacerbations. 102/196 (52.04%) patients of COPD yielded organisms in culture, of which 101 had exacerbations of varying degrees. None of the samples were positive for L.pneumophila in culture. PCR was found to be positive in 11 and 22 numbers for M. pneumoniae and L.pneumophila respectively. Serology was positive in 19.89 % of M. pneumoniae , 17.3 % of C. pneumoniae and 8.67 % of L. pneumophila . Conclusions The present study found bacterial pathogens, including atypical bacteria, in 60.10 % of cases. 30.6% were atypical bacteria. Hence, the antibiotic regimen recommended for AECOPD should include an antibiotic directed at atypical bacteria. No one method is suitable for the detection of atypical bacteria. Therefore, atypical pathogens should be diagnosed using a combination of tests for better sensitivity.