Isolation, Identification of A Swine-derived Streptococcus dysgalactiae subsp. equisimilis

Abstract

【Objective】Streptococcus dysgalactiae causes joint swelling and dyskinesia in pigs, which greatly reduces feed remuneration and economic benefits of pig farms. Recent studies suggest that Streptococcus dysgalactiae subsp. equisimilis is also a potential zoonosis pathogen. This study not only provides data for the prevention and treatment of S. dysgalactiae equinoides from pigs, but also has public health significance.【Method】Several piglets in a large-scale pig farm in Guangdong Province showed swollen joints and claudication symptoms in March 2022. In order to determine the cause of the disease, according to the results of clinical autopsy, the joint fluid of the diseased piglets was sampled aseptically for bacterial isolation and culture, morphological observation of dominant bacteria, biochemical identification, 16S rDNA gene sequence analysis, drug sensitivity test and mouse pathogenicity test, and PCR identification of virulence genes,【Result】According to the morphological and physical and chemical characteristics of the isolated strain, combined with 16S rDNA sequencing and online BLAST analysis results, it was identified as S. dysgalactiae subsp. equisimilis. The results of antibiotic sensitivity test showed that the isolated strains were sensitive to ceftriaxone, cefaclor, penicillin G, cefalexin, cefepime, ciprofloxacin, sulfamethoxazole, spectinomycin and enrofloxacin, less sensitive to amikacin, doxycycline, polymyxin B, norfloxacin and ampicillin, while resistant to kanamycin, gentamicin, streptomycin, lincomycin and amoxicillin. PCR identification of virulence gene showed that the genotype of the isolated strain was eno + napr + cfb - lmb + bca - bac - scpB + cyl +. The result of mouse pathogenicity test showed that the isolated strain caused visceral lesions and death in mice, showing significant pathogenicity.【Conclusion】This is the first report on pathogenic S. dysgalactiae from swine in South China, which provides reference for the prevention and treatment of clinical S. dysgalactiae from swine.

Keywords

• streptococcus dysgalactiae subsp. equisimilis
• isolation and identification
• drug sensitivity test
• pathogenicity
• south china