| BackgroudStreptococcus suis, is an important zoonosis pathogen. According to the diversity of bacterial capsular polysaccharides, S. suis strains are divided into 35 serotypes. The serotype 2 strains are the most virulent pathogens that infection human and pig in the world, they are also the most common pathogenic serotype in China. Recent S. suis has been receiving growing attention not only for its role in severe and increasingly reported in humans, but also for its involvement in drug resistance. Therefore, studise on the resistance and molecular epidemiology of S. suis serotype 2 strains isolated from Jiangsu can contribute to treatment and prevention of people infected with S. suis in this region.Methods 1. Since 1998 to 2010, collected S. suis serotype 2 strains that infection humans and pigs and related epidemiological data from Jiangsu Province.2. According to the American Clinical and Laboratory Standards Institute Institute, K-B methods were used for 14 kinds of drug susceptibility analysis.3. Detected antibiotic resistance genes of macrolide antibiotic (ermA、ermB and mefA), tetracycline (tet(M), tet(O)、tet(W)、tet(OW/32/O)、tet(L)、tet(K) and transposon Tn916) and aminoglycoside (Aph3’) by conventional PCR.4. Detected virulence genes (cps, mrp, ef, sly, gapdh, fbps) of S. suis by using PCR to know S. suis serotype 2 strains isolated from Jiangsu are as virulent isolates.5. Using Multilocus sequence typing and Multiple-locus variable number tandem repeat analysis methods to analysied S. suis serotype 2 strains and cluster analysis with domestic and foreign reference strains.Results1. From 1998 to 2010,27 S. suis serotype 2 strains were isolated from patients’ blood (19/27,70.4%), dead pigs and related pork products (8/27,29.6%) and collected.2. S. suis serotype 2 strains isolated from Jiangsu were resistant against streptomycin (100%), tetracycline (100%), cotrimoxazole (40.74%) erythromycin (11.11%) and azithromycin (7.41%). All Jiangsu strains were sensitive to penicillin, cephalosporins and fluoroquinolones.3. In this study, we detected resistance gene tet(M) in 26 strains; resistance gene tet(O) in 1 strain; transposon Tn916 in all strains. We can not found resistance gene Aph3’, ermA, ermB and mefA in all strains.4. The identity of the isolates were confirmed as virulent strains by positive PCR for the genes for the cps2j, mrp, ef, sly, gapdh and fbps of S. suis serotype 2.5.In this study,26 strains were ST7 (1-1-1-1-1-1-3), only one strain was ST1 (1-1-1-1-1-1-1) by MLST method.6. In this study, all strains were divided into 13 genotypes, most allelic number differences were focused on TR9.Conclusion1. From 1998 to 2010,27 S. suis serotype 2 isolates were collected in Jiangsu. Of which 10 strains were isolated in 1998 and 5 strains were isolated in 2005. These are the years that emergence of human infected S. suis serotype 2 outbreak in China. The biggest number of strains were isolated in Nantong, which the more emphasis, experienced and attention on local government, health department, agriculture department, also may be the situation that infected with S. suis in pigs in Nantong is more serious.2. The S. suis serotype 2 strains isolated from Jiangsu were resistant against aminoglycosides, tetracycline, macrolides and sulfa drugs. The four antibiotics were widespread used even abuse in pig industry in the world.In this study, we found tetracycline resistance gene (tet) which coding ribosomal protection proteins in all strains, this results is consistent with the phenotypic results. In this study, we could not found aminoglycoside resistance gene(Aph3’) and macrolide resistance gene (ermA、ermB and mefA) in all strains, it may be associated with other drug-related resistance gene or other resistance mechanism.3. In this study, the identity of the isolates were confirmed as virulent strains by positive PCR for the genes for the cps2j, mrp, ef, sly, gapdh and fbps of S. suis serotype 2.4. The results of this study showed that all strains were ST7 except JS-26 by MLST, this type is caused outbreak in Jiangsu in 1998 and outbreak in Sichuan in 2005, it is also the dominant genotype in China. One strain (JS-26) isolated from Nantong in 2010 was ST1 by MLST, and another strain isolated from Yancheng in 2014 was also ST1, the results indicating that ST1 and ST7 strains were exist in Jiangsu. We should pay more attention to the genotype of S. suis serotype 2 in later surveillance.5. MLVA had higher resolution in this study. The cluster analysis was consistent with the epidemiological investigations, the results indicating that MLVA can used for pathogen trace-back. |
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