Bacterial, Antimicrobial, and Clinical Profile of Multidrug-Resistant Gram-Negative Bacilli Isolates From Intensive...

Background Multidrug-resistant (MDR) Gram-negative bacilli (GNB) are a major cause of healthcare-associated infections in intensive care units (ICUs), leading to increased morbidity, mortality, and limited treatment options. This study was conducted to determine the prevalence of MDR-GNB among ICU clinical specimens and to evaluate their antimicrobial susceptibility patterns. Material and methods This cross-sectional observational study was carried out at the Department of Microbiology, Krishna Institute of Medical Sciences, Karad, from August 2024 to March 2025. A total of 370 clinical specimens obtained from ICU patients were processed using standard microbiological methods. The VITEK 2 compact automated system (Marcy-l'Étoile, France: bioMérieux) was used to identify Gram-negative bacilli, and VITEK 2 AST cards were used for antibiotic susceptibility testing. Multidrug-resistant isolates were defined as resistance to three or more antimicrobial classes. Results A total of 370 specimens were processed; growth was observed in 228 specimens. Among these, 109 were Gram-positive, and 119 were Gram-negative. Multidrug-resistant Gram-negative bacteria were identified in 101 isolates. The highest burden of infection was observed in both the 31-40 year and 41-50 year age groups, with each group contributing 26 cases (25.74%). Males were more frequently affected than females, contributing 69 (68.32%) cases compared to 32 (31.68%). Among the pathogens, Pseudomonas aeruginosa was the most commonly isolated organism (31, 30.69%), followed by Klebsiella spp. (25, 24.75%), and Klebsiella pneumoniae (18, 17.82%). Escherichia coli (12, 11.88%) and Acinetobacter spp. (11, 10.89%), were also notable contributors. Urine was the predominant specimen source (43, 42.57%), followed by endotracheal tube samples (22, 21.78%), wound swabs (10, 9.90%), sputum (9, 8.91%), and blood (9, 8.91%). Antimicrobial resistance was high for meropenem (96, 95.05%), netilmicin (94, 93.07%), amikacin (93, 92.08%), and ceftazidime (92, 91.09%). In contrast, nitrofurantoin showed the lowest resistance (5, 11.63%) and the highest susceptibility (38, 88.37%) among urine isolates. The second most effective antimicrobial combination was piperacillin/tazobactam, with susceptibility observed in 34 (33.66%) isolates. These findings indicate a significant prevalence of MDR-GNB infections among middle-aged male intensive care unit (ICU) patients, with limited effective treatment options. Conclusion This study demonstrates a high prevalence of multidrug-resistant Gram-negative bacilli among patients in the intensive care unit with Pseudomonas aeruginosa, Klebsiella spp., Acinetobacter spp., and Escherichia coli as the predominant pathogens. The predominance of urine and respiratory specimens may be associated with the frequent use of urinary catheters and mechanical ventilation in critically ill ICU patients, contributing to hospital-acquired infections. The high level of resistance across multiple antimicrobial classes, including carbapenems, aminoglycosides, cephalosporins, fluoroquinolones, and piperacillin/tazobactam, highlights the challenge of having few options for treatment. These results show the urgent need for early microbiological diagnosis, culture, and susceptibility-guided therapy; strict methods for infection prevention and control; and robust antimicrobial stewardship programs to reduce the burden of MDR infections and improve patient outcomes in the ICU.