Streptococcus gallolyticus is often found as a member of the normal gut microflora in various animals. However, it has been reported to cause mastitis in cattle, septicaemia in pigeons, and meningitis, septicaemia and endocarditis in humans. However, little is known about the epidemiology and crucial virulence factors of S. gallolyticus. To help address these issues, we developed a multilocus sequence typing (MLST) scheme for S. gallolyticus. Seven housekeeping gene fragments were sequenced from each of 58 S. gallolyticus isolates collected from diverse origins and sources. The MLST scheme had good discriminatory ability. The 63 strains, including the 5 whole genome sequenced strains examined, resolved into 57 sequence types (STs), with 52 STs represented by only a single strain. With respect to the identification of S. gallolyticus subspecies (i.e. S. gallolyticus subsp. gallolyticus, S. gallolyticus subsp. pasteurianus and S. gallolyticus subsp. macedonicus), the results of biochemical tests and DNA-DNA hybridization were in high concordance with those of the MLST scheme. The MLST scheme developed in this study may be a useful tool capable of replacing the conventional methods used for S. gallolyticus subspecies identification. The results of this study suggest that the biology and virulence of two pathogenic S. gallolyticus subspecies (i.e. S. gallolyticus subsp. gallolyticus and S. gallolyticus subsp. pasteurianus) are very different. The MLST scheme offers researchers a valuable typing tool that will promote further investigation of the epidemiology of S. gallolyticus.
Streptococcus parasuis has recently been removed taxonomically from Streptococcus suis, a zoonotic pathogen. S. parasuis has been detected
in healthy pigs and in diseased pigs, which suggests that S. parasuis is involved in the normal microbiota of pigs and has potential pathogenicity. However, the
pathogenicity of S. parasuis in pigs is unclear because of the lack of appropriate detection methods that discriminate S. parasuis from S.
suis. In this study, we developed a PCR method that is specific for S. parasuis. The detection limit of the PCR was 350 CFU per reaction. Bacteria isolated from
the saliva of eight pigs were collected and examined by PCR. Sixty-four isolates positive for PCR were obtained from the samples of all pigs. Thirteen of the 64 isolates were genetically
confirmed as S. parasuis, and biologically and biochemically had nearly the same features of known S. parasuis strains, which suggested that strains
positive for PCR were S. parasuis. Among the 64 isolates, 28 isolates were serotypes 20, 22, or 26 in the S. suis serotyping scheme. The remaining 36
isolates were untypeable, which suggested the presence of novel serotypes or a capsule-negative form. Therefore, the PCR method described in this study is a useful tool for identifying
S. parasuis, and can be used in etiological studies on this bacterium.
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