Biofilm production ability and other microbiological features of Streptococcus canis

Tetracycline, Macrolide and Lincosamide Resistance in Streptococcus canis Strains from Companion Animals and Its Genetic Determinants

Growing antimicrobial resistance (AMR) in companion-animal pathogens, including Streptococcus canis (S. canis), is a significant concern for pet treatment as well for public health. Despite the importance of S. canis in veterinary and human medicine, studies concerning the AMR of this bacterium are still scarce. A total of 65 S. canis strains, isolated from dogs and cats, were assessed to test for susceptibility to six clinically relevant antimicrobials via a microdilution method. The prevalence of the selected acquired-resistance genes was also investigated via PCR. High MIC50 and MIC90 values (≥128 μg/mL) were noted for tetracycline, erythromycin and clindamycin. Only a few strains were resistant to the tested beta-lactams (6.2%). Tetracycline resistance was found in 66.2% of the strains. Resistance to erythromycin and clindamycin (ML resistance) was found in 55.4% of the strains. Strains with a phenotype showing concurrent resistance to tetracycline and ML were predominant (53.8%). AMR in the tested S. canis strains was associated with a variety of acquired and potentially transferable genes. Tetracycline resistance was conferred by tet(O) (40.0%), tet(M) (9.2%), and tet(T) (1.5%), which is reported for the first time in S. canis. In most cases, the tet(M) gene was detected in relation to the conjugative transposon Tn916. The MLSB phenotype was confirmed in the strains harboring erm(B) (43.1%) and erm(TR) (7.7%). To conclude, a high rate of S. canis strains occurring in dogs and cats displayed resistance to antimicrobials important for treatment; moreover, they are a potential reservoirs of various resistance determinants. Therefore, AMR in these pathogens should be continuously monitored, especially regarding the One Health concept.

Genotypic and phenotypic features of eye-origin Streptococcus canis isolates from dogs in 2021: relatedness with clonal complex 46 and antimicrobial resistance

Eye (including cornea) and ear canal are major sources of Streptococcus canis in companion animal practice. We aimed to clarify genotypic and phenotypic features of the eye-origin isolates in 2021 compared to ear-origin isolates in 2021 and eye-origin isolates in 2017. Of the 102 isolates in 2021, nine eye-origin isolates were enrolled, whereas twenty-one ear-origin isolates in 2021 and thirteen eye-origin isolates in 2017 were included as controls. Genotypic analyses included virulence-associated gene (VAG; inl, sagA, slo, scp, lbp, fbp, gbp, ap1, fp1, and brp) profiling, S. canis M-like protein (SCM) allele typing, multilocus sequence typing, and antimicrobial resistance (AMR) genotyping: phenotypic analyses contained hemolytic activity (HA) measurement and AMR phenotyping. There was only one 2017-eye-origin isolate with high-level HA, while the others showed low-level HA. We observed no association of the 2021-eye-origin population with detection rate of each VAG. There was no association of the 2021-eye-origin population with main SCM allele 2. We found significant association of the 2021-eye-origin population with main clonal complex (CC) 46 containing sequence type (ST) 46/ST2. There was significant association of the 2021-eye-origin population with AMR phenotypes/genotypes. Our observations suggest the unique microbiological features (CC46 having AMR phenotypes/genotypes) among the 2021-eye-origin population.

Comparative genomic features of Streptococcus canis based on the pan-genome orthologous group analysis according to sequence type

Using bacterial pan-genome obtained through whole genome sequencing (WGS), coding DNA sequences (CDSs) can be clustered into pan-genome orthologous groups (POGs). We aimed to investigate comparative genomic features of Streptococcus canis based on POG analysis and to determine CDSs specific to prevalent sequence type (ST) 9. Twenty WGS datasets on S. canis strains from invasive and non-invasive specimens were retrieved from the National Center for Biotechnology Information Assembly database. Based on the WGS data, we performed comparative genome hybridization (CGH), pan- and core-genome prediction, Venn diagram test with five ST9 strains, and phylogenetic analysis, with ST determination. We compared the CDSs between seven ST9 and 13 non-ST9 strains. We observed genomic diversity based on CGH and Venn diagram. The predicted pan- and core-genomes contained 4,772 and 1,403 genes, respectively. We found five clades consisting of different STs (ST1, ST44/2, ST13/14, ST21/15/41, and ST9) based on phylogenetic tree. There were differences in four pathways (DNA restriction-modification system, DNA-mediated transposition, extracellular region, and response to oxidative stress) regulated by CDSs specific to ST9. Our findings describe genomic diversity in CGH and Venn diagram, pan- and core-genomes, five clades of genomes consisting of different STs, and unique CDS features associated to ST9.