Association between agr group, genetic background, virulence factors and disease types of Staphylococcus aureus isolated from Chinese children

Abstract

Background Staphylococcus aureus (S. aureus) accessory gene regulator (agr) system plays a critical role in staphylococcal pathogenesis. Our study aimed to investigate the relationship between agr group, the genetic background, virulence genes and disease types distribution of S. aureus isolated from different clinical sources among Chinese children.Methods S. aureus strains were isolated from Beijing Children’s hospital from October 2017 to October 2019. Isolates were typed by multilocus sequence typing (MLST), staphylococcal protein A (spa), agr, and staphylococcal cassette chromosome mec (SCCmec) typing (for methicillin-resistant S. aureus [MRSA] isolates). Furthermore, all isolates were tested for the presence of 19 selected virulence genes.Results A total of 191 non-repetitive S. aureus clinical isolates were collected and the agr type I was the most prevalent (84.8%). S. aureus isolates were divided into 33 sequence types (STs), 20 clonal complexes (CCs) and 59 spa types, ST59 (39.8%) and t437 (37.7%) were the predominant types. CC59, CC25, CC22, CC951, CC8, and CC398 isolates possessed agr group I; CC15 isolates harbored agr group II; CC30 strains were characterized as agr group III, and CC121 harbored agr group IV. Of the 19 virulence genes, the tst gene was more prevalent among agr group III compared to other groups (p = 0.006); eta and etb genes were more prevalent among agr group IV than other groups (p = 0.003 and 0.001, respectively); nearly all strains that harbored the lukS/F-PV gene (98.3%) belonged to agr group I (p = 0.004); the frequencies of bbp and ebpS genes belonged to agr group I were statistically lower than that of other groups (p < 0.001). Among 161 diagnoses, the frequency of strains from cellulitis patient harbored agr group III was higher than that of other groups (p = 0.046), and one strain isolated from staphylococcal scalded skin syndrome (SSSS) patient, which was identified as agr type IV (p = 0.021).Conclusions The results indicated that the S. aureus agr type was linked to the genetic background. Besides, a possible relationship between the agr group, several virulence determinants, and specific disease types was observed.