Prevalence and Antimicrobial Resistance Pattern of Serratia marcescens in Respiratory Samples from ICU Patients: A Six Months Prospective Study

Background and study aim: Serratia marcescens has emerged as a significant nosocomial pathogen in intensive care units (ICUs), particularly causing ventilator-associated pneumonia and respiratory tract infections. This study conducted to determine the prevalence and antimicrobial resistance pattern of S. marcescens in respiratory samples from ICU patients and to describe the associated clinical characteristics.Patients and Methods: This prospective observational study was conducted at a tertiary-care super speciality hospital in New Delhi, over 6 months from January to July 2025. Two hundred respiratory samples (endotracheal aspirates, bronchoalveolar lavage, and sputum) from ICU patients were processed for bacterial culture. Automated systems were employed for bacterial identification and antimicrobial susceptibility testing.Results: Out of 200 respiratory samples analyzed, S. marcescens was isolated from 19 samples (9.5%). The organism was most commonly isolated from endotracheal aspirates (63.2%) followed by bronchoalveolar lavage (26.3%). The isolates demonstrated high resistance to ampicillin (100%), cefazolin (94.7%), and trimethoprim-sulfamethoxazole (84.2%). Carbapenem resistance was detected in 26.3% of isolates. Mortality rate in patients with S. marcescens respiratory infections was 31.6%.Conclusion: S. marcescens represents a significant cause of respiratory tract infections in ICU patients with concerning antimicrobial resistance rates. Implementation of stringent infection control measures and antimicrobial stewardship programs is crucial for managing these infections.