Staphylococcus aureus is associated with bloodstream infections and has a well-known ability to develop antimicrobial resistance. The COVID-19 pandemic significantly impacted bacterial resistance patterns, particularly in hospital settings, due to increased empirical antibiotic use, healthcare system overload, and prolonged hospital stays. This study aimed to analyze the incidence density and the profiles of methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA, respectively) isolated from blood cultures.

A retrospective study was conducted in a high-complexity hospital in southern Brazil, including clinical isolates of S. aureus bacteremia collected between 2014 and 2023 (pre- and post-pandemic contexts). Data were extracted from the hospital’s laboratory information system.

The incidence coefficient of MSSA was higher than that of MRSA throughout the study period, with a peak of 0.71 per 1,000 patient-days in 2021, a critical year of the COVID-19 pandemic. The average incidence density of MRSAremained relatively stable at approximately 0.30 per 1,000 patient-days. The increased MSSA incidence deviates from the expected trend observed in other studies. When comparing the pre-pandemic period (January 2014 to February 2020) with the pandemic/post-pandemic period (March 2020 to December 2023), a significant increase in MSSA resistance to erythromycin, clindamycin, and sulfamethoxazole-trimethoprim was observed, with erythromycin resistance reaching 56.1%. In contrast, among MRSA isolates, resistance patterns remained stable, except for clindamycin, which showed a significant reduction in resistance during the same period.

This study revealed distinct variations in S. aureus incidence and resistance patterns. The observed increase in MSSA resistance to other antimicrobials highlights the importance of continuous microbiological surveillance and the implementation of effective antimicrobial stewardship strategies, particularly in public health crisis scenarios.