UNLABELLED

The objective of this research was to investigate the genomic epidemiology of methicillin-resistant (MRSA) in a pediatric population in Shanghai, China. Whole-genome sequencing was conducted for 492 randomly selected MRSA isolates obtained from a pediatric hospital between 2013 and 2022. ST59 (37.4%), ST398 (22.4%), ST88 (5.7%), and ST22 (5.5%) were the predominant lineages among these children. While ST59 maintained a dominant annual proportion before 2017, the proportion of ST398 gradually increased from 2013 to 2016, with ST398 ultimately emerging as a prevalent clone with a proportion comparable to that of ST59 after 2017. Among the prevalent STs, the -SCC structure also experienced dynamic changes. Within ST59, the t437-IV subtype experienced a decline and has even been replaced by t172-IV in recent years. In ST398, the t011-V subtype appeared in 2014 and rapidly became the leading subtype. The antibiotic resistance profiles and virulence factors exhibited clone-related features. Compared with other prevalent lineages, ST59 presented high resistance to erythromycin and clindamycin, whereas ST398 presented relatively low resistance to common antimicrobial agents and fewer virulence determinants. Panton-Valentine leucocidin was more common in ST338 and ST1232, whereas toxic shock syndrome toxin was closely associated with ST1 and ST5. The MRSA cases could also be classified into community- and hospital-associated cases, with highly significant differences between the two in terms of demographic characteristics, clindamycin susceptibility, and virulence genes. In conclusion, this study revealed high genetic diversity and dynamic changes in the molecular epidemiology of pediatric MRSA isolates from Shanghai collected over a decade.

IMPORTANCE

Methicillin-resistant (MRSA) has emerged as a significant global health concern. Previous research on MRSA epidemiology has predominantly focused on adult populations or targeted specific infection sites, while there was limited research on the long-term evolution of MRSA from the pediatric population. This study addresses this knowledge gap by conducting a comprehensive, 10-year surveillance of pediatric MRSA isolates using whole-genome sequencing. We characterized the molecular typing, as well as the phenotypic and genotypic antimicrobial resistance profiles, and virulence factors present in MRSA isolates obtained from children. Our results highlight the imperative for continuous, vigilant monitoring of MRSA within the pediatric demographic to track its evolving genetic landscape.