Bacterial Aetiology of Community Acquired Pneumonia in a Tertiary Care Hospital of Southern India

Introduction: Community Acquired Pneumonia (CAP) is associated with high morbidity and mortality worldwide. Knowledge of common microbial patterns in CAP is crucial for making initial therapeutic decisions for empiric antimicrobial treatment. Aim: To determine the bacterial aetiology of CAP among hospitalised patients in a tertiary care hospital of Southern India. Materials and Methods: A descriptive study was carried out among 220 adult subjects, enrolled from a period of August 2012 to August 2014, admitted to a tertiary care hospital of Southern India, with a provisional diagnosis of CAP. Subjects were recruited based on chest radiography and clinical criteria. Blood, sputum, pleural fluid, Bronchoalveolar Lavage (BAL) and tracheal aspirates were obtained for microbiological investigations. Antimicrobial susceptibility testing was carried out on Streptococcus pneumoniae and Staphylococcus aureus isolates. The clinical specimens were further subjected to Polymerase Chain Reaction (PCR) to confirm the bacterial aetiology of S.pneumoniae and Haemophilus influenzae. Study data were summarised by frequency and percentage using SPSS (Statistical Package for Social Sciences) version 16.0. Results: A total of 220 subjects who were diagnosed for CAP of which 154 (70%) were culture negative and 66 (30%) were culture positive cases of CAP. The most commonly isolated pathogens were 29 (44%) of S.pneumoniae followed by 21 (32%) of S.aureus, 10 (15%) of H.influenzae and 6 (9%) of Klebsiella pneumoniae. Resistance to penicillin occurred in 24 ( 82.75%) of S.pneumoniae isolates. Methicillin-Resistant Staphylococcus aureus (MRSA) was demonstrated among 10 (48%) of the 21 total S.aureus CAP cases. Conclusion: Culture-based aetiologic diagnosis of CAP was made in only one-third of the cases. Ongoing antimicrobial resistance surveillance to S.pneumoniae and S. aureus is recommended. Determining the resistance profile of Klebsiella pneumoniae and H.influenzae is needed as pneumonia caused due to Gram negative aetiology is rising in the community setting. Rapid screening of bacterial CAP pathogens from clinical samples using PCR may be beneficial for clinicians to make a prudent antibiotic choice for CAP.