Comparison between Invasive and Non-invasive Streptococcus agalactiae Isolates from Human Adults, Based on Virulence Gene Profile, Capsular Genotype, Sequence Type, and Antimicrobial Resistance Pattern.

This study assessed whether invasive group B Streptococcus (GBS) isolates were similar to non-invasive isolates from adult patients. Invasive and non-invasive GBS isolates were collected from three hospitals and two laboratory centers from January 2015 to October 2019. The isolates were identified through 16S rRNA amplicon sequencing and amplification of GBS-specific dltS. The virulence gene profile, capsular genotype, sequence type (ST)/clonal complex (CC), and antimicrobial resistance (AMR) phenotype/genotype were determined, and the 72 invasive isolates and 50 non-invasive isolates were comparatively analyzed. We observed a significantly decreased rate of rib detection in the invasive isolates compared to that in the non-invasive isolates (77.8% vs. 92.0%, p < 0.05). Additionally, we found significant differences in the prevalence of CC1 (23.6% vs. 46.0%, p < 0.05) and CC26 (12.5% vs. 2.0%, p < 0.05) between the invasive and non-invasive populations. However, there were no significant differences in the comparative data of the virulence gene profiles, capsular genotypes, other STs/CCs, and AMR phenotypes/genotypes between the two populations. These findings suggest that the invasive and non-invasive isolates shared similar features in terms of virulence gene profile, capsular genotype, ST/CC, and AMR genotype/phenotype (except for the rates of rib detection and CC1/CC26 prevalence).