Staphylococcus aureus: changes in antimicrobial sensitivity profile and its relationship with SCCmec among clinical isolates

Background and Objectives: Staphylococcus aureus is a pathogen of great clinical relevance, especially those resistant to methicillin, called MRSA. Over the years, S. aureus antimicrobial resistance patterns have changed. Understanding such changes is essential to update protocols and propose efficient therapeutic approaches. This study aimed to characterize the temporal distribution of S. aureus antimicrobial resistance in patients admitted to the hospital as well as to assess its relationship with SCCmec typing. Methods: a total of 9,949 cultures of clinical materials were analyzed, between January 2000 and October 2019, from patients admitted to a university hospital in southern Brazil. All isolates had their identification and antimicrobial sensitivity profile analyzed using manual and automated techniques. Furthermore, 86 isolates were selected for mecA gene research and SCCmec typing using conventional and multiplex PCR techniques, respectively. Results: when assessing the temporal distribution of S. aureus over 20 years, it was possible to observe a drop in the proportion of MRSA compared to methicillin-sensitive S. aureus (MSSA). Between 2000 and 2002, the frequency of MRSA was 58.5%, whereas that of MSSA was 36.7%. However, from 2003 onwards, there was a reversal of these percentages. At the end of the analyzed period, 55.2% of infections were caused by MSSA, whereas 36.2% contained MRSA isolates. Furthermore, in the period analyzed, the highest prevalence was of SCCmec type II. Conclusion: these data suggest an epidemiological change in S. aureus from clinical materials, with a change in the prevalent type of SCCmec and changes in the antimicrobial sensitivity profile exhibited by the isolates. Such facts must be considered by the clinical staff with a focus on effective patient management, the choice of appropriate antimicrobial therapy so that effective infection control measures are implemented.