Publication:

Bacterial etiology and multidrug resistance patterns in hospital-acquired pneumonia: predominance of Gram-negative pathogens

Background Hospital-acquired pneumonia (HAP) is a major nosocomial infection and is increasingly complicated by multidrug-resistant (MDR) pathogens. Center-specific data on bacterial etiology and susceptibility patterns are essential to optimize empiric therapy and antimicrobial stewardship. Objective was to determine bacterial etiology and MDR burden in HAP, and to describe organism-specific antibiotic susceptibility patterns, emphasizing Gram-negative predominance.

Methods This cross-sectional study enrolled 100 adult inpatients with HAP (onset ≥48 hours after admission) in the department of respiratory medicine, Bangladesh Medical University, Dhaka, over 12 months, from August 2024 to August 2025. Sputum, induced sputum, or bronchoalveolar lavage specimens were cultured following quality screening, and antimicrobial susceptibility testing was performed by disc diffusion. Results were summarized using frequencies and percentages; MDR was defined as non-susceptibility to at least one agent in three or more antimicrobial classes.

Results Bacterial growth was obtained in 78.0% of cases, with single-organism isolation in 68.0% and polymicrobial growth in 10.0%. A total of 89 isolates were recovered, predominantly Gram-negative (93.3%). Leading pathogens were Klebsiella spp. (33.7%), Pseudomonas aeruginosa (31.5%), and Acinetobacter spp. (24.7%). Overall MDR prevalence was 87.8%. Cephalosporin susceptibility was low among major Gram-negative organisms, while carbapenem susceptibility was moderate; colistin susceptibility varied across species.

Conclusions HAP in this cohort was dominated by MDR Gram-negative pathogens with limited susceptibility to commonly used antibiotics, supporting the need for local antibiograms and stewardship-guided empiric therapy.