Antimicrobial Resistance of Non-Fermenting Gram-Negative Bacilli in a Multidisciplinary Hospital in Romania.

Background: Antimicrobial resistance (AMR) in Acinetobacter spp., Pseudomonas spp., and Stenotrophomonas maltophilia poses a significant risk in healthcare-associated infections. Constant monitoring using quantitative metrics is necessary to direct empirical treatment. Methods: We conducted a retrospective observational study at the Fundeni Clinical Institute, Bucharest, Romania, analysing antibiogram data from January 2021 to December 2024. Over 200,000 microbiological records were screened, and 1189 isolates of the three targeted pathogens were included. The Multiple Antibiotic Resistance Index (MARI) was applied to evaluate selective pressure across years, hospital departments, sample types, and hospitalisation categories. Results:Acinetobacter baumannii and Pseudomonas aeruginosa exhibited the highest resistance levels, with median MARI values exceeding 0.25 in 2024, particularly in Intensive Care and Transplant units. In contrast, S. maltophilia showed lower overall MARI values, though resistance variability increased in 2024 (extremes up to 0.30). Notably, resistance to carbapenems in Acinetobacter spp. rebounded in 2024, while Pseudomonas spp. demonstrated a favourable trend of decreasing resistance to several β-lactams. Conclusion: Our findings underscore significant interspecies differences in AMR dynamics and highlight the utility of MARI as a valuable operational indicator. Ongoing local surveillance is needed for refining empirical treatment protocols and informing antimicrobial stewardship in Romanian hospitals.