Identification of six novel capsular polysaccharide loci ( NCL ) from Streptococcus suis multidrug resistant non‐typeable strains and the pathogenic characteristic of strains carrying new NCL s

Abstract

Streptococcus suis is a major swine pathogen and an important zoonotic agent worldwide. At least nine serotypes can infect human so far. Although 29 serotypes (1–19, 21, 23–25, 27–31 and 1/2) strains are considered as authentic S. suis, a novel variant serotype Chz and strains carrying 20 novel capsular polysaccharide loci (NCL) have been identified recently. However, information about pathogenic and antimicrobial resistance characteristics of strains carrying NCLs is still unavailable. In this study, we identified six new NCLs (designated as NCL21‐26) from 35 non‐typeable S. suis strains by agglutination tests and whole genome sequencing analysis. Further analysis of the genetic context of NCL25 and NCL26 showed a mosaic structure of the capsular polysaccharide loci. NCL25 exhibited considerable similarity to that of serotypes 10 and 11, and NCL26 shared similarity to that of serotype 9 and NCL4. Antimicrobial susceptibility testing demonstrated that strains carrying NCL21‐26 were all resistant to clindamycin, lincomycin, erythromycin, tilmicosin and tetracycline. Animal infection experiments showed that the virulence of NCL26 strain NJ1112 isolated from a disease pig was similar to that of S. suis serotype 2 virulent strain SC070731 in both zebrafish and mouse infection models, highlighting the necessity for surveillance of strains belonging to NCL26. We also developed a multiplex PCR assay to detect NCL21‐26 strains. Our findings expand the views of genetic diversity of S. suis capsular polysaccharide loci and S. suis pathogenic characteristic.

Update on Streptococcus suis Research and Prevention in the Era of Antimicrobial Restriction: 4th International Workshop on S. suis

“…In addition to the "classical" described serotypes, a novel variant (serotype Chz) and strains carrying 26 novel capsular polysaccharide loci (NCL1-26) have been identified recently [28][29][30][31][32]. These findings expand the views of the genetic diversity of S. suis cps loci.…”

Genomic and pathogenic investigations of Streptococcus suis serotype 7 population derived from a human patient and pigs

“…Most virulence-associated genes preferentially present in highly pathogenic S. suis serotype 2 strains were absent from all serotype 7 genomes. Previous studies also reported that these virulence markers studied in S. suis serotype 2 strains were not suitable as virulence markers for S. suis non-serotype 2 strains [ 3 , 12 , 44 ]. Thus, S. suis serotype 7 virulent strains may utilize a different pathogenesis strategy.…”

Update on the Mechanisms of Antibiotic Resistance and the Mobile Resistome in the Emerging Zoonotic Pathogen Streptococcus suis

“…The serotype distribution can also change with time in the same territory. A new very virulent serotype, the Chz serotype, responsible for meningitis in pigs, seems to have emerged in recent years, and 20 new cps loci (NCL) have been identified in non-typeable isolates [ 12 , 13 ]. Strains of S. suis can also be classified into three groups according to their pathotypes: (i) a “non-clinical” group for strains originating from the upper respiratory tract microbiota that do not trigger symptoms or cause the death of its host, (ii) a “respiratory” or “possibly opportunistic” group of strains generally sampled in lungs from clinically sick animals or from clinically healthy animals in farms that have suffered from outbreaks of S. suis , and (iii) a “pathogenic” or “systemic” group of strains obtained from samples of blood nervous and/or articular systems and identified as the causes of infection [ 14 , 15 ].…”