Carbapenem and Multidrug Resistance Among Gram-Negative Bacilli in a County Emergency Clinical Hospital from Western Romania: A Retrospective Study, 2024–2025

Background and Objectives: Antimicrobial resistance among Gram-negative bacilli is a major clinical challenge, particularly in hospitals where carbapenem-resistant and multidrug-resistant organisms limit therapeutic options. This study aimed to characterize the distribution and resistance profiles of Gram-negative bacilli isolated in a university-affiliated hospital in western Romania during 2024–2025, focusing on temporal variation, intensive care unit (ICU) origin, carbapenem resistance, and multidrug resistance (MDR). Materials and Methods: This retrospective, single-center study included 8931 Gram-negative isolates recovered from clinical specimens between January 2024 and December 2025. Bacterial identification was performed using the VITEK 2 Compact system and/or MALDI-TOF mass spectrometry, whereas antimicrobial susceptibility testing was performed using the VITEK 2 system and interpreted according to EUCAST criteria. Carbapenem resistance was defined as resistance to meropenem, imipenem, or ertapenem for Enterobacterales and to meropenem or imipenem for Pseudomonas aeruginosa and Acinetobacter baumannii. MDR was defined as resistance to at least one agent in at least three antimicrobial classes. Factors associated with MDR were evaluated using multivariable logistic regression. Results: Escherichia coli was the most frequent isolate (36.0%), followed by Klebsiella pneumoniae (22.8%), P. aeruginosa (9.6%), A. baumannii (9.4%), and Proteus mirabilis (8.0%). Among 8708 isolates evaluable for both outcomes, carbapenem resistance was 30.8% and MDR was 44.5%; both were significantly more frequent in 2025 than in 2024. ICU isolates showed higher carbapenem resistance (56.1% vs. 18.0%) and MDR (65.3% vs. 33.9%) than non-ICU isolates. A. baumannii had the highest burden, with 87.4% carbapenem resistance and 87.5% MDR. MDR was independently associated with study year, ICU origin, age group, sex, specimen type, and bacterial species; the strongest association was observed for A. baumannii versus E. coli (adjusted OR 23.45, 95% CI 18.38–29.91). Conclusions: Carbapenem resistance and MDR were frequent, particularly among ICU isolates and high-risk pathogens. The findings support intensified local surveillance, antimicrobial stewardship, and targeted infection prevention and control measures.