Low GAS carriage in school-aged children in western China during the national atypical scarlet fever resurgence: Insights from two cross-sectional studies

Abstract

Introduction

This study examined group A streptococcus(GAS) carriage, emm types, and antibiotic susceptibility in children (6–13 years) in Aral, China, during the post-COVID-19 scarlet fever resurgence, providing regional insights.

Methods

The prevalence of GAS carriage was assessed in 1,835 children aged 6–13 years across two surveys at an Aral school in China during the post-COVID-19 resurgence of scarlet fever. GAS isolates were analyzed for emm types, M1_UK lineage, and antimicrobial susceptibility using culture, PCR, sequencing, and automated methods.

Results

The first survey (885 children) showed a 1.9% isolation rate, highest in 9-year-olds (4.8%) and slightly higher in boys (2.3% vs. 1.5%, P > 0.05). The second survey (950 children) reported a 3.1% rate, peaking at 10 years (6.7%) and also higher in boys (3.5% vs. 2.6%, P > 0.05). Colonization rates were similar overall (P > 0.05), but increased significantly in children aged ≥10 years (1.1% to 3.3%, P = 0.038). No children tested positive for GAS in both sampling rounds, which meant that the two surveys identified distinct host populations colonized by the bacteria. Emm12 prevalence decreased from 76.5% to 55.2% (P > 0.05), while emm1 increased from 11.8% to 31.0% (P > 0.05), with no M1_UK lineage detected. All isolates were sensitive to penicillin, linezolid, vancomycin, and levofloxacin. Among 33 co-resistant isolates, emm12 accounted for 84.8% and emm1 for 15.2%.

Conclusion

Despite low GAS carriage rates, variations in age distribution and emm types suggest increased bacterial activity, warranting ongoing monitoring for GAS-related diseases.