Epidemiology, evolution and cryptic susceptibility of methicillin-resistant Staphylococcus aureus in China: a whole-genome-based survey

Objectives: The aim of this study was to investigate the genomic epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in China to identify predominant lineages and their associations with clinical data and antimicrobial resistance profiles. Methods: We performed a national prevalence study of patients with S. aureus infections in 22 tertiary hospitals in China from 2015 to 2017. Clinical data from patients and the antimicrobial phenotypes were collected for each isolate. Genome sequencing was performed on a proportion of isolates and a phylogenetic analysis was undertaken. Genotypic and phenotypic beta -lactam susceptibilities were compared. Results: A total of 1900 patients with S. aureus infections were included, of which 40% involved MRSA. Community-associated MRSA (CA-MRSA) infections were 24% of the total isolates. Genomic data showed that more than three-quarters of the MRSA were from three dominant lineages CC239 (25%, 116/471), CC5 (21%, 96/471) and CC59 (33%, 154/471) with CC59 accounting for more than half of the CA-MRSA isolates. Penicillin susceptibility genomic features were observed in 53% (251/470) of MRSA, including almost all of the CC59 (152/154) lineage, and 96% (242/251) of these isolates demonstrated in vitro susceptibility to penicillin or amoxicillin combined with clavulanic acid. Phylogenetic analysis indicated that the CC59 lineage can be divided into six lineages with all Asian CC59 isolates likely arising from an ancestral Mainland China lineage. Conclusions: This study showed a high prevalence of CA-MRSA in China, largely due to the widespread presence of CC59. As almost all isolates in this lineage possess genetic variants leading to increased beta-lactam susceptibility, we suggest that to improve antibiotic stewardship combinations of penicillins and beta-lactamase inhibitors should be included in the antibiotic susceptibility testing panels used to inform treatment decisions and research undertaken on this combination therapy. (C) 2021 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the genomic epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in China and found a high prevalence of the CC59 lineage in community-associated MRSA. Almost all isolates in the CC59 lineage showed genetic variants leading to increased beta-lactam susceptibility, suggesting potential for improved antibiotic stewardship.