Antimicrobial Resistance Profiles of Bacterial Pathogens Associated with Acute Diarrheal Disease: A Three-Year Retrospective Study in a Romanian Tertiary-Care Hospital

Background: Despite its typically self-limiting course, acute diarrheal disease continues to be clinically relevant from an antimicrobial resistance surveillance perspective. In-depth analyses at a national level remain limited, with available Romanian studies from the last decade focusing on individual pathogens, often relying on a restricted isolate collection. In this context, we aimed to evaluate antimicrobial resistance profiles and distribution of Salmonella spp., Campylobacter spp., Escherichia coli, Yersinia spp. and Shigella spp. Methods: Data was obtained from records from the Microbiology Laboratory of a tertiary-care hospital serving the south region of Romania, over a 3-year period. Results: Campylobacter spp. had high resistance rates to ciprofloxacin (81.65% for C. jejuni; 85.15% for C. coli) and tetracycline (44.65% for C. jejuni; 56.07% for C. coli). Erythromycin resistance remained low and stable over the study period, with no statistically significant temporal variation; however, C. coli isolates demonstrated significantly higher erythromycin (p = 0.001) and tetracycline (p = 0.008) resistance rates compared to C. jejuni. Overall Salmonella spp. resistance rate to ciprofloxacin was 46.00%, with higher resistance observed in serogroups C (63.64%) and D (52.53%) (p < 0.01). Ampicillin (AMP) resistance varied significantly across years and serogroups, with serogroup B consistently demonstrating higher resistance rates (40.48%) (p < 0.001). E. coli isolates reacting with pathotype-associated O antisera revealed high resistance levels to ampicillin (41.57%), amoxicillin–clavulanic acid (AMC) (38.73%) and sulfamethoxazole–trimethoprim (SXT) (19.25%), with low resistance levels to ciprofloxacin (9.04%) and ceftriaxone (CRO) (9.71%); no significant variation in resistance patterns was identified across years or serological pools, suggesting a relatively stable resistance profile over the study period. Yersinia spp. isolates showed no notable antimicrobial resistance levels. Shigella spp. isolates exhibited high resistance for ampicillin (78.57%), sulfamethoxazole–trimethoprim (68.75%), amoxicillin–clavulanic acid (50.00%) and ceftriaxone (35.41%). Conclusions: This study addressed a recognized gap in Romanian and Eastern European surveillance data and aims to contribute to a stronger evidence base for future epidemiological investigations and antimicrobial stewardship efforts. Resistance rates identified in our study may provide valuable information for comparison with data generated from veterinary, food and environmental surveillance programs, thereby supporting a more comprehensive understanding of antimicrobial resistance (AMR) epidemiology. These findings may additionally contribute to the development of coordinated strategies aimed at mitigating the emergence and spread of AMR.