Active Surveillance, Drug Resistance, and Genotypic Profiling of Staphylococcus aureus Among School-Age Children in China

Abstract

Methicillin-susceptible (MSSA) and methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) nasal colonization predisposes individuals for endogenous infections and is a major threat to children. Recently, oxacillin/cefoxitin-susceptible <i>mecA</i>-positive <i>S. aureus</i> (OS-MRSA) has been reported worldwide. Herein, a prospective, cross-sectional study was conducted across five schools, representing three educational stages, in Guangzhou, China. Nasal swabs from 2,375 students were cultured for <i>S. aureus</i> and all isolates were subjected to antibiotic susceptibility testing phenotypically and confirmed by <i>femB</i> and <i>mecA</i> genetic detection; all the isolates were classified as MSSA, MRSA, or OS-MRSA. All strains were also analyzed by multi-locus sequence typing. Among the 2,375 swabs, <i>S. aureus</i> was detected in 744 children (31.3%, 95% CI: 25.9-36.7%), of whom 72 had MRSA (3.0%, 95% CI: 0.6-5.4%) and 4 had OS-MRSA (0.2%, 95% CI: 0.1-0.3%), of which an oxacillin- and cefoxitin-susceptible MRSA strain was identified. The prevalence of <i>S. aureus</i> and MRSA was higher in younger children. The highest percentage of drug resistance of the <i>S. aureus</i> isolates (<i>n</i> = 744) was to penicillin (85.5%), followed by erythromycin (43.3%) and clidamycin (41.0%). The most prevalent sequence types (STs) were ST30, ST45, and ST188 in MSSA, accounting for 38.7% of the total isolates, whereas ST45, ST59, and ST338 accounted for 74.6% of the MRSA isolates and ST338 accounted for 50.0% of the OS-MRSA isolates. The MRSA and OS-MRSA isolates (<i>n</i> = 76) were grouped into three clades and one singleton, with clonal complex (CC) 45 as the most predominant linkage. The top nine multi-locus sequence typing-based CCs (CC30, CC45, CC5, CC1, CC15, CC944, CC398, CC59, CC7) represented 86.7% of all <i>S. aureus</i> isolates. All CC30 isolates were resistant to erythromycin and clidamycin, and almost all these isolates were also resistant to penicillin (99.2%). The CC45 and CC59 isolates exhibited high resistance rates to oxacillin at 31.5 and 59.0%, respectively. This study provides updated data valuable for designing effective control strategies to mitigate the burden of disease and to improve the adequacy of empirical antimicrobial treatments for potentially harmful infections.