Biofilm production ability of Streptococcus dysgalactiae subsp. equisimilis: relatedness with host, Lancefield group, source, clonal complex, and virulence-associated gene.

We assessed biofilm production ability (BPA) of noninvasive Streptococcus dysgalactiae subsp. equisimilis (SDSE) from humans/companion animals and determined relationships between BPA populations and other host/microbiological features. Sixty-four companion animal-/human-origin isolates were collected with host information. We measured BPA using crystal violet staining, along with doing emm typing, multilocus sequence typing, and antimicrobial resistance (AMR) phenotyping/genotyping, and detection of virulence-associated genes (VAGs) (prtF1-prtF2-lmb-cbp-sicG-srtp1-srtp2-brpA). Significant difference in BPA of SDSE from different hosts/sources and with different Lancefield groups was assessed. We analyzed associations between BPA populations (strong/moderate/weak/no biofilm producers) and emm types, sequence types/clonal complexes (CCs), AMR phenotypes/genotypes, and VAG types. Seventeen, twenty-four, and twelve isolates belonged to strong, moderate, and weak biofilm producers: eleven showed no BPA. There was a difference in BPA distributions between human- and animal-origins and between groups G and C isolates. We found an association of BPA populations with eye/ear source (vs. pus/skin source). There was a relationship between BPA populations and CC127 (vs. CC17). We observed no associations of BPA populations with AMR phenotype/genotype. There was an association of BPA distributions with srtp1 detection. Our observations suggest potential associations of BPA with host, Lancefield group, source, CC, or VAG.