Antimicrobial Resistance in Gram-negative Pathogens Isolated from Blood Cultures of Intensive Care Unit Patients: A Hospital-based Cross-sectional Study

Introduction: Intensive Care Units (ICUs) are considered the “epicentre of infections.” In developing countries, Antimicrobial Resistance (AMR) has emerged as a major healthcare concern. Infections, including bloodstream infections caused by Gramnegative bacteria (GNB), are usually higher among ICU patients. Owing to their distinctive cell wall structure, GNB are often more resistant to antimicrobial agents compared to their Grampositive counterparts. Aim: To determine the pattern of AMR among GNB, isolated from blood cultures of patients admitted to ICUs of a tertiary care hospital. Materials and Methods: This cross-sectional study was conducted over a period of two years (January 2023-December 2024) in the Department of Microbiology, Byramjee Jeejeebhoy Government Medical College and Sassoon General Hospital, Pune, Maharashtra, India. A total of 247 GNB isolated from positive blood cultures were included in the study. These isolates were identified up to the species level using standard microbiological procedures, including Gram staining, motility testing, and biochemical tests. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method. Patients’ demographic details were recorded and analysed. Results were interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines (2023, M100). Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 24.0 (IBM, USA), and a p-value <0.05 was considered as statistically significant. Results: Out of the 247 GNB, Klebsiella pneumoniae (68; 27.5%), followed by Escherichia coli (51; 20.6%), were the most common pathogens isolated from blood cultures. Isolation of K. pneumoniae was significantly higher in the Medical ICU (MICU) compared to other ICUs. K. pneumoniae demonstrated high resistance to almost all classes of antimicrobials. Colistin resistance was observed in two isolates of K. pneumoniae and in one isolate each of Pseudomonas aeruginosa and Acinetobacter spp. GNB pathogens from blood cultures of MICU patients showed significantly high resistance to different classes of antimicrobial agents. Conclusion: AMR among GNB isolated from bloodstream infections in ICU patients is alarmingly high. As AMR rates vary widely based on geographical region and healthcare settings, it is essential for each healthcare facility to determine its own AMR patterns. This will enable the implementation of appropriate strategies to prevent and control the emergence and spread of drug-resistant pathogens, particularly among critically ill patients.