Spectrum of Lower Respiratory Bacterial Pathogens and their Antimicrobial Susceptibility in a Tertiary Care Hospital at Rawalpindi

Objective: To study the spectrum of bacterial etiological agents causing lower respiratory tract infections and their antimicrobial susceptibility pattern in a tertiary care hospital at Rawalpindi. Methodology: A descriptive, cross-sectional study was conducted in the department of Microbiology, Armed Forces Institute of Pathology (AFIP), Rawalpindi from June to December 2021. Total 130 patients with lower respiratory tract infections (LRTIs) irrespective of age and gender were included in the study while patients of pulmonary tuberculosis, fungal diseases and patients having prior antibiotic therapy before sample collection were excluded. Non quantitative cultures were performed for sputum, non- directed bronchial lavage (NBL), pleural fluid and quantitative cultures for bronchoalveolar lavage (BAL) and endobronchial (EB) washings specimens. Antibiotic susceptibility was performed using Clinical and Laboratory Standards Institute (CLSI) 2021 guidelines. Results: Pseudomonas aeruginosa (26.9%) was found to be the most prevalent bacterial pathogen followed by Klebsiella pneumoniae (23%). Both Gram negative and Gram-positive bacteria showed highest antimicrobial resistance to flouroquinolones. Gram negative bacteria were more susceptible to aminoglycosides and carbapenems. Gram positive bacteria were most susceptible to linezolid and vancomycin. Staphylococcus aureus was isolated from 8 samples, of which 5(62.5%) were Methicillin-resistant Staphylococcus aureus (MRSA). Conclusion: This study concluded that the most frequent bacterial pathogen causing lower respiratory tract infections was Pseudomonas aeruginosa and both Gram negative and Gram-positive bacteria showed highest antimicrobial resistance to flouroquinolones.