Epidemiology, Molecular Characteristics of Methicillin-Resistant Staphylococcus Aureus in China: A Multicenter Longitudinal Study Based on Whole-Genome Sequencing

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominantly linages and their associated antimicrobial resistance and virulence profiles. In this study, we conducted whole-genome sequencing (WGS) on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing staphylococcal cassette chromosome mec (SCC mec) typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%), ST5-t2460-II (6.0%). Of note, CC8, the predominant lineage in 2014-2015, was replaced by CC59 in 2016-2017 and since then alternately dominant with CC5. Interestingly, the complicated dynamic change of CC5 population structure was observed with ST764-t1084-II, ST5-t2460-II, ST764-t1084-II and ST764-t002-II successively dominant. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA less resistance to most tested antimicrobial and relatively lower methicillin MIC, while ciprofloxacin, sulfamethoxazole/trimethoprim and rifampicin resistance was closely linked with CC8. MRSA isolates conservatively carried multiple virulence genes for capsule, exoenzymes, secretion, iron uptake and metabolism, biofilm formation and hemolysis. PVL encoding genes was markedly more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was found to be most predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China in order to monitor changes in MRSA epidemiology. Funding Information: This study was funded by grants from the Natural Science Fund of China (82072343). Declaration of Interests: The authors declare that there are no conflicts of interest.