Abstract:
In order to understand the serotype, virulence genotype and drug resistance of the epidemic strains of Streptococcus suis in Sichuan Province, in this experiment, 151 lung tissue samples from dead pigs in pig farms in some areas of Sichuan Province were collected from 2021 to 2022; the strains suspected of Streptococcus suis were isolated and identified, and the isolated strains of Streptococcus suis were carried out for serotyping identification, and virulence factor(sly, mrp, epf) test and susceptibility test were performed on the typed strains of Streptococcus suis. The results showed that among the 151 lung tissue samples, a total of 32 strains of Streptococcus suis were isolated and identified. Among the 32 isolated strains of Streptococcus suis, 24 strains were typed, belonging to 8 serotypes, of which 10 were serotype 16, accounting for 31.2%, being the dominant serotype. There were 7 strains for serotype 2, accounting for 21.9%; 2 strains for serotype 9, accounting for 6.3%; one strain each for type 1, 4, 5, 7 and 30, each accounting for 3.1%; there were 8 un-typed strains, accounting for 25.0%. A total of 5 virulence genotypes were detected in 24 typed strains, namely sly+mrp-epf-(11/24), sly+mrp+epf+(1/24), sly-mrp-epf-(8/24), sly-mrp+epf+(1/24), sly+mrp+epf-(3/24); and the dominant virulence genotype was sly+mrp-epf-. 24 strains of Streptococcus suis had the highest resistance rate to lincomycin, which was 100%; this was followed by clindamycin and florfenicol(91.7%), and the lowest resistance to cefpirome(37.5%). The overall resistance of 24 strains of Streptococcus suis was serious, of which 20 strains showed multi-drug resistance, accounting for 83.3%; one strain was 8-resistant, that was, resistant to all 8 classes of antibiotics in this test. The results suggested that there were multiple serotypes of Streptococcus suis in Sichuan Province, of which types 16 and 2 were the main serotypes, and sly+mrp-epf-was the dominant virulence genotype; and the overall drug resistance was serious, and most of the strains were multi-drug-resistant.