Eleven-Year Trends in Antimicrobial Resistance and Outcomes Among Hospitalized Adults with Positive Enterococcus Cultures

Background: Enterococcal infections are major healthcare-associated infections associated with increasing antimicrobial resistance and substantial mortality. However, long-term epidemiological data integrating antimicrobial resistance trends with clinical outcomes remain limited in Saudi Arabia. This study evaluated antimicrobial resistance trends, clinical characteristics, and mortality among patients with enterococcal positive cultures over an 11-year period. Methods: We conducted a single-center retrospective cohort study of 2272 hospitalized adults with culture-positive Enterococcus spp. between March 2015 and November 2025. Demographic, clinical, microbiological, and outcome data were extracted from electronic medical records. Temporal resistance trends and independent predictors of in-hospital mortality were evaluated using logistic regression. Results: Enterococcus faecalis accounted for 74.1% of isolates. Vancomycin-resistant enterococci (VRE) prevalence showed no significant temporal trend during the study period, with an overall prevalence of 11.3%, whereas high-level gentamicin resistance declined significantly (OR per year 0.933, 95% CI 0.903–0.964; p < 0.001). Multidrug resistance showed no significant temporal change. Compared with E. faecalis, E. faecium exhibited substantially higher resistance to vancomycin, ampicillin, and ciprofloxacin, while susceptibility to linezolid, daptomycin, and tigecycline remained above 95%. Overall, in-hospital mortality was 15.6% and was independently associated with age ≥60 years, intensive care unit admission, bloodstream infection, coinfection, and E. faecium positive culture. Conclusions: This study provides one of the largest long-term evaluations of enterococcal positive culture in Saudi Arabia, demonstrating stable VRE prevalence, declining high-level aminoglycoside resistance, and persistent species-specific differences in antimicrobial resistance and mortality. These findings support local antimicrobial resistance surveillance and antimicrobial stewardship efforts by providing updated epidemiological data on enterococcal positive cultures.