Microbial Etiology and Antibiotic Resistance Patterns in Hospital- Acquired Pneumonia: A Cross-Sectional Analysis

Abstract

Background: Hospital-acquired pneumonia (HAP) is a major cause of morbidity and mortality in hospitalized patients, particularly in intensive care units (ICUs). The emergence of multidrug-resistant (MDR) pathogens complicates treatment and increases healthcare burdens. Identifying the microbial etiology and antibiotic resistance patterns is essential for guiding effective empirical therapy and infection control measures. Objective: This study aimed to determine the microbial etiology and antibiotic resistance patterns among patients diagnosed with HAP at Mahaveer Institute of Medical Science and Research, Bhopal, over a one-year period. Methods: A hospital-based, cross-sectional study was conducted from December 2023 to November 2024. Respiratory specimens, including sputum, endotracheal aspirates, and bronchoalveolar lavage, were collected from 200 patients meeting the clinical criteria for HAP.
Standard microbiological techniques were used for bacterial isolation and identification, with further confirmation of MDR isolates using the VITEK-2 system. Antibiotic susceptibility testing was performed using the Kirby-Bauer disk diffusion method, and minimum inhibitory concentrations (MICs) were determined for resistant isolates. Methicillin-resistant Staphylococcus aureus (MRSA) was identified using cefoxitin disk testing, while carbapenem resistance was confirmed using the modified Hodge test or Carba NP test. Results: The most commonly isolated pathogens were Klebsiella pneumoniae (35%), Pseudomonas aeruginosa (25%), Acinetobacter baumannii (20%), Escherichia coli (10%), and Staphylococcus aureus (10%). A high prevalence of MDR pathogens was observed, with
carbapenem resistance detected in Klebsiella pneumoniae (65%) and Acinetobacter baumannii (60%). ESBL production was noted in 75% of Klebsiella pneumoniae and 40% of Escherichia coli isolates. MRSA accounted for 8% of Staphylococcus aureus cases. Colistin and tigecycline demonstrated the highest efficacy against MDR Gram-negative bacteria, while vancomycin remained effective against MRSA. Conclusion: The study highlights a significant burden of MDR pathogens in HAP cases, with high levels of carbapenem and cephalosporin resistance. The findings emphasize the need for stringent infection control measures, antimicrobial stewardship programs, and continuous surveillance of resistance patterns to optimize empirical therapy and improve patient outcomes.