Abstract:

Objective To analyze the serotypes，drug resistance and virulence gene carrying status of invasive group B Streptococcus（GBS） in newborns in Wenzhou，and to provide references for the diagnosis and treatment of neonatal GBS infection. Methods Totally，54 GBS isolates isolated from sterile sites of newborns in Class 3 Grade A hospitals in Wenzhou from 2019 to 2023 were collected. The isolates were identified，and in vitro drug susceptibility test was performed. The drug sensitivity tests were conducted，and high-throughput whole-genome sequencing（WGS） and multi-locus sequence typing（MLST） were performed. Results All the 54 GBS isolates were sensitive to penicillin，ampicillin，vancomycin and linezolid. The drug resistance rate to tetracycline was 87.3%，and the drug resistance rates to clindamycin and levofloxacin were 55.6% and 13.0%，respectively. A total of 7 serotypes were determined，with type Ⅲ being the predominant one（46.2%，25/54）. A total of 14 ST types were determined，with ST17 being the predominant one（24.1%，13/54）. The carrying rates of adhesion-related genes pavA，fbsA，lmb and srr2 were 100.0%，76.0%，87.0% and 27.8%，respectively. The carrying rates of invasion-related genes hylB，cylK，cylJ，cylI，cylE，cylA，cylZ，cylG，cylD，cylF，acpC and cylB were all 100.0%，while the carrying rates of cylX and CAMP were 90.7% and 96.3%，respectively. The carrying rate of immune evasion-related gene rib was 48.1%，and the carrying rates of neuA，neuB and neuC were all 100.0%. Conclusions The GBS isolates causing neonatal infections have a high resistance rate to tetracycline and clindamycin，and the carrying rates of virulence genes are also high.

Key words: Group B Streptococcus, Drug resistance, Virulence gene, Multi-locus sequence typing, Newborn, Wenzhou