Background: Empirical antibiotic therapy is the mainstay of management of adult community-acquired pneumonia (CAP) globally. Knowledge of prevalent pathogen (bacterial) profile and drug susceptibility pattern is very essential for appropriate management of CAP cases, which again calls for regular update of pathogen profile in a given locality. This study was to identify the bacterial etiology of CAP cases and their antibiotic susceptibility pattern. Methods: This cross-sectional study was done on adult CAP patients from medicine, respiratory medicine, and intensive care unit area in our tertiary care hospital between May 1, 2015, and October 30, 2016. Subjects were enrolled continuously, and expectorated sputum, bronchoalveolar lavage fluid, and blood culture were performed. Urine antigen test was done for Streptococcus pneumoniae and Legionella pneumophila . Three types of ELISA (IgM, IgG, and IgA) were performed for atypical agents ( Mycoplasma , Chlamydia , and Legionella ) of CAP. Isolates obtained from culture of Sputum/BAL/Blood were further processed for antibiotic susceptibility testing - by disc diffusion as well as E-test method (latter for MIC i.e. minimum inhibitory concentration, determination). Results: About 574 subjects were included, and in 266 (46.3%) cases, bacterial pathogen could be detected. Klebsiella pneumoniae (33.6%) and S. pneumoniae (32.9%) were the predominant agents identified. Atypical agents ( Mycoplasma , Legionella , and Chlamydia ) were at 15.1%. A high proportion of pneumococci isolates were multidrug resistant (52.6%). Resistance to beta-lactams, macrolide, and other agents was on the higher side, but fluoroquinolones were found to be less resistant (15.8%–21.1%). Extended-spectrum beta-lactamase (among Klebsiella isolates) and methicillin-resistant Staphylococcus aureus were also detected. Conclusion: A moderate-to-high degree of drug-resistant in adult CAP was evident, which is detrimental in effective empirical management of such cases. Urgent implementation of antibiotic stewardship scheme is the need of the hour.

Atypical agents such as Mycoplasma, Legionella, Chlamydia species, and Coxiella burnetii (Q-fever agent) are responsible for some adult community-acquired pneumonia (CAP). Insufficient studies on this topic can be blamed for the failure to include atypical pathogens in empirical management. We followed adult CAP cases for two years, and samples (respiratory and serum) were tested by culture, ELISA (IgM, IgG, and IgA), and PCR. A risk factor analysis was performed. Overall in 21.3% adult CAP patients, atypical agents found were Mycoplasma pneumoniae (51.5%), Legionella pneumophila (28.8%), and Chlamydophila pneumoniae (19.7%). However, amongst patients <60 years of age and in the summer season, the proportion of atypical agents increased significantly. There is thus a need to re-examine empirical antibiotic regimes.