Epidemiological trends and antimicrobial susceptibility profiles of clinical Staphylococcus aureus isolates: A single-center experience

Aims: Staphylococcus aureus (S. aureus), particularly methicillin-resistant S. aureus (MRSA), is a high-priority pathogen, and local long-term data are limited.This study aimed to evaluate MRSA distribution and antimicrobial resistance trends among clinical S. aureus isolates over five years. Methods:In this retrospective, single-center study, the first S. aureus isolate per patient from diagnostic clinical specimens at a tertiary-care hospital between 2021 and 2025 was included; surveillance screening specimens were excluded.The primary endpoints were the proportion of MRSA and resistance to individual antimicrobial agents.Results: The study included 391 isolates from 391 patients.The median age was 51.9 years (interquartile range: 28.3-70.9),and 196 of the patients were female (50.1%).MRSA accounted for 92 isolates (23.5%), with no difference by age group, sex, specimen type, or clinical unit (all p>0.05).Compared with methicillin-susceptible S. aureus (MSSA), MRSA isolates were more frequently resistant to fluoroquinolones, erythromycin, fusidic acid, tetracycline, trimethoprim-sulfamethoxazole, and gentamicin (all p<0.001), but not to clindamycin (p=0.210).No isolate was resistant to vancomycin, linezolid, or rifampicin.From 2021 to 2025, resistance increased for ciprofloxacin (7.4% to 26.5%; p<0.001), erythromycin (p=0.013),clindamycin (p=0.024), and fusidic acid (p=0.028).Calendar year was independently associated with methicillin resistance (adjusted odds ratio 1.27 per year; p=0.017).Multidrug resistance was more frequent in MRSA than MSSA isolates (55.4% vs. 3.0%; p<0.001). Conclusions:In this center, MRSA accounted for about one quarter of clinical isolates and increased over time.Methicillin resistance was associated with resistance to nonbeta-lactam antimicrobial agents and with multidrug resistance, and resistance to ciprofloxacin, erythromycin, and clindamycin increased.