Changes in Antimicrobial Resistance of Staphylococci Isolated from Bloodstream Infection and the Impact of COVID-19

Objective To analyze the changes in antimicrobial resistance of Staphylococcus aureus ( S. aureus ) and coagulase-negative staphylococci (CoNS) in bloodstream infections (BSIs) bloodstream infections (BSIs) between 2018 and 2024, and to assess the impact of the COVID-19 pandemic on these trends. Methods A total of 575 S. aureus and 1,014 CoNS isolates were retrospectively reviewed. Demographic characteristics and resistance rates to 16 antimicrobial agents were compared. Statistical analyses included the chi-square ( χ ² ) test and Mann-Kendall trend analysis. Results CoNS infections were more common in minors and the elderly, while S. aureus predominated in young and middle-aged adults. CoNS exhibited higher resistance rates to most antimicrobials compared to S. aureus , with Methicillin-Resistant CoNS (MRCNS) detection rates exceeding 70%. An increasing trend in resistance was observed for penicillin G in S. aureus and for fluoroquinolones in CoNS. Following the COVID-19 pandemic, resistance rates to several agents—such as penicillin G, clindamycin, and ciprofloxacin—further increased in both groups. No resistance to linezolid, vancomycin, or tigecycline was detected. Conclusion The resistance profile of staphylococci in bloodstream infections has intensified, with the COVID-19 pandemic contributing to increased resistance rates for certain antimicrobials. Continuous surveillance is essential to guide appropriate antimicrobial therapy.