Bacteriology of Lower Respiratory Tract Samples with Antibiotic Susceptibility Patterns at a Tertiary Care Hospital in Karachi

Lower respiratory tract infections are widespread in Pakistan. Determining sensitivity is crucial to combat increasing antimicrobial resistance. Objectives: To ascertain the prevalence of bacterial pathogens isolated in lower respiratory tract samples and the antimicrobial susceptibility patterns of these pathogens in one of the tertiary care hospitals in Karachi. Methods: This study was a prospective observational study that took place for six months. Three hundred and thirty-five positive respiratory samples of patients with clinical LRTIs were collected. Identification of the bacteria was conducted by the standard microbiological procedures, and the determination of antimicrobial resistance was conducted by the Kirby-Bauer disk diffusion test according to the guidelines of CLSI 2025. SPSS version 26.0 was used to analyze data. The chi-square test was applied, and a p-value <0.050 was deemed significant. Results: The study examined 335 culture-positive patient isolates, revealing Gram-negative rods (GNR) as the predominant pathogens (n=275), mainly Klebsiella spp., Acinetobacter spp., and Pseudomonas aeruginosa. Gram-positive cocci (GPC) (n=38) included Staphylococcus aureus and Streptococcus pneumoniae, while Nocardia was identified among gram-positive rods (n=22). Organism type significantly influenced resistance patterns (p<0.001), but specimen type did not (p=0.401). Conclusions: The most common LRTI pathogens were Klebsiella spp., Acinetobacter spp., and Pseudomonas aeruginosa that exhibited a wide spectrum of multidrug resistance. Stringent antibiotic stewardship plays a crucial role in preventing further increases in resistance.