Biofilm production ability and associated characteristics of Streptococcus agalactiae isolates from companion animals and humans.

Abstract

OBJECTIVE\nWe evaluated biofilm production ability (BPA) of Streptococcus agalactiae isolates from companion animals/humans and clarified the relationship between BPA populations and other microbiological features.\n\n\nMETHODS\nCompanion animal-/human-origin isolates were collected with host information. We measured BPA using crystal violet staining, via virulence-associated gene profiling (hylB-pavA-pilB-spb1-srtC1-brpA), capsular genotyping, multilocus sequence typing, and antimicrobial resistance (AMR) phenotyping/genotyping. Significant difference in BPA of isolates from different hosts was assessed. We analyzed the association between BPA populations and the virulence genotypes, capsular genotypes, sequence types/clonal complexes, and AMR phenotypes/genotypes. Inhibitory effect of berberine on BPA was evaluated.\n\n\nRESULTS\nFive, twenty-six, and twenty-six isolates belonged to strong, moderate, and weak biofilm producers, whereas seventeen showed no biofilm production. We defined strong, moderate, or weak biofilm producers as the producer group (n\xa0=\xa057) to conduct a comparative analysis between the producer and non-producer populations. There was a significant correlation between the producer population and vaginal specimen. We found significant associations between the producer group and presence (57.9%) of pilB and between the non-producer population and presence (70.6%) of spb1. There was no association between the producer group and capsular genotypes, sequence types/clonal complexes, and AMR phenotypes/genotypes (except for a significant correlation between the producer group and AMR to minocycline). We confirmed inhibitory effect of berberine at sub-minimum inhibitory concentrations (MICs) against the type strain on BPA.\n\n\nCONCLUSION\nOur observations suggest that S. agalactiae harboring pilB is more capable of producing biofilms, with berberine inhibitory effect at sub-MICs on BPA.