The pathogenic and antimicrobial resistance characteristics of Streptococcus suis isolates from healthy pigs at slaughterhouses in Jiangsu Province,2023
[Objective]Streptococcus suis is a prevalent pathogen attacking pigs and a zoonotic agent.In 1998,an outbreak of S.suis infection in Jiangsu caused numerous pig deaths and 14 human deaths.Therefore,investigating S.suis infections in healthy pigs from slaughterhouses in Jiangsu is crucial for public health.[Methods]Tonsils were collected from healthy pigs in slaughterhouses of Jiangsu in 2023,and S.suis was isolated,identified,and serotyped.The pathogenicity of S.suis isolates to zebrafish and mouse models was examined.Furthermore,the antibiotic resistance characteristics and genes and the antimicrobial susceptibility of the isolates were identified and evaluated.[Results]The positive rate of S.suis in the samples collected from Kunshan in July 2023 was 50.85％(30/59).A total of 62 strains were isolated from the samples collected from Kunshan,and serotype 31(12.90％,8/62)had the highest isolation rate,followed by serotype 19(11.29％,7/62)and serotype NCL2(8.06％,5/62).In the samples collected from Danyang in July and November 2023,the positive rate of S.suis was 60.71％(34/56),and 77 strains were isolated.Serotype 16 had the highest isolation rate of 11.69％(9/77),followed by serotype 9(10.39％,8/77),serotype 21(10.39％,8/77),and serotype 31(10.39％,8/77).The isolates from both regions exhibited high resistance to lincosamides(98.56％,137/139),macrolides(95.68％,133/139),and tetracyclines(96.40％,134/139).Furthermore,97.84％(136/139)of strains were multi-drug resistant.All the strains were sensitive to cefotaxime and vancomycin.According to the sources and serotypes,we selected 42 representative strains(18 from Kunshan and 24 from Danyang)to perform zebrafish infection experiments.At a dose of 3×106 CFU/fish,seven strains exhibited high pathogenicity to zebrafish,causing the mortality rates ≥80.00％.Three strains(serotypes 1,3,and 23)causing mortality rates ≥80.00％in zebrafish and comparable to the virulent strain SC070731 were selected for mouse infection experiments.All the three strains led to the mortality rates ≥80.00％in mice.[Conclusion]The healthy pigs in Jiangsu have a high carrying rate of S.suis(55.65％,64/115),and 97.84％(136/139)of the isolates are multi-drug resistant.Strains of serotypes 1,3,and 23 exhibited strong pathogenicity.
万方数据
维普
