Comparison of Molecular Characteristics Between Methicillin-Resistant and -Susceptible Staphylococcus aureus Clinical Isolates by Whole-Genome Sequencing

INTRODUCTION: The transmission of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) are great public health concern worldwide. To better understand S. aureus evolution and dissemination, we compared the molecular features of MSSA and MRSA isolates. METHODS: In this study, 74 MSSA and 102 MRSA non-duplicate isolates were recovered from clinical samples between 2016 and 2020. Molecular epidemiology, antimicrobial resistance determinants, and virulence gene profiles were carried out by whole-genome sequencing (WGS). RESULTS: Twenty distinct sequence types were identified in MRSA isolates, with the most common being ST59, ST630, and ST338. The major genotypes of MSSA were ST188 and ST7. The toxin genes clfA, sek, and seq were significantly associated with MRSA, while splA/B, clfB, map, sdrC/D, and sem-sen-seo-seu were detected more frequently in MSSA isolates than MRSA (P < 0.05). The tst positive isolates were more commonly identified in CC1 and CC72, whereas lukE/D was mainly found in the CC7, CC15, CC88, and completely absent in CC59 clones. CONCLUSION: Our results compared the genetic diversity between MRSA and MSSA strains, suggesting efforts to fight infections caused by MSSA need to be intensified due to MSSA isolates carrying wide range of virulence factors. Comparative epidemiological studies of large populations of MSSA and MRSA will be necessary in the future to understand how MSSA and MRSA populations may co-evolve and interact in the future.