一株猪源停乳链球菌类马亚种的分离鉴定

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

【目的】停乳链球菌(Streptococcus dysgalactiae)可引起猪关节肿大和运动障碍,大大降低饲料报酬和猪场经济效益,近年研究提示停乳链球菌类马亚种(Streptococcus dysgalactiae subsp.equisimilis)是一种潜在的人兽共患病病原。对猪源停乳链球菌类马亚种进行研究,可为防治该病提供数据,具有公共卫生意义。【方法】2022年3月广东省某规模化猪场出现仔猪关节肿大和跛行症状。为确定病因,无菌采集发病仔猪关节液进行细菌分离培养,对优势菌进行形态观察、生化鉴定、16S rDNA基因序列分析、小鼠致病性试验及抗生素敏感性试验,并对其毒力基因进行PCR鉴定。【结果】根据分离菌株的形态特征、生化特性,结合16S rDNA序列测定与在线BLAST分析结果,确定其为链球菌属的停乳链球菌类马亚种。药敏试验结果表明,分离菌株对头孢曲松、头孢克洛、青霉素G、头孢氨苄、头孢吡肟、环丙沙星、磺胺异恶唑、大观霉素、恩诺沙星敏感,对丁胺卡那、多西环素、多粘菌素B、诺氟沙星、氨苄西林次敏感,而对卡那霉素、庆大霉素、链霉素、林可霉素、阿莫西林表现出耐药性。毒力基因PCR鉴定结果表明,分离菌株的基因型为eno+napr+cfb-lmb+bca-bac-scpB+cyl+。小鼠致病性试验结果表明,分离菌株导致小鼠内脏病变和死亡,具有显著的致病性。【结论】首次报道了华南地区有关致病性猪源停乳链球菌病例,研究结果为临床猪源停乳链球菌病的防治提供参考。

【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.