【摘要】 从湖北省某猪场呈现链球菌急性死亡症状的保育猪中分离病原菌，通过细菌培养、形态学观察、生化鉴定及分子生物学分析进行鉴定。结果表明，病料接种含5%绵羊血的TSA培养基后，分离出革兰阳性链状排列球菌，经猪链球菌9型特异性引物PCR扩增及序列比对，确诊为猪链球菌9型，命名为XF-1菌株。毒力基因检测显示，该菌株携带fbps、orf、sly、gapdh 4种毒力基因，而epf与mrp基因为阴性。药敏试验表明，XF-1菌株对头孢呋辛、头孢噻呋、氨苄西林中度敏感，对头孢噻吩、庆大霉素等12种抗生素耐药。小鼠致病性试验证实其强毒力，以≥5×10~8CFU/只剂量攻毒后7 d内全部死亡（20×10~8、10×10~8、5×10~8CFU/只），1×10~8CFU组死亡率40%，死亡小鼠脏器分离菌经PCR复核与XF-1菌株一致。更多还原

【Abstract】 The pathogenic bacteria was isolated from nursery piglets exhibiting acute fatal symptoms of streptococcosis at a pig farm in Hubei Province. The pathogen was identified through bacterial culture,morphological observation,biochemical tests,and molecular analysis. After inoculating clinical samples onto TSA medium supplemented with 5% sheep blood,Gram-positive cocci arranged in chains were isolated. PCR amplification using serotype 9-specific primers and subsequent sequencing confirmed the isolate as Streptococcus suis serotype 9,designated strain XF-1. Virulence gene screening revealed that XF-1 carried fbps,orf,sly,and gapdh genes,while epf and mrp genes were negative. Antimicrobial susceptibility testing indicated intermediate sensitivity to cefuroxime,ceftiofur,and ampicillin,but resistance to 12 antibiotics including cephalothin and gentamicin. Mouse pathogenicity trials demonstrated high virulence,all mice challenged with ≥5×10~8 CFU died within 7 days(groups 20×10~8,10×10~8,and 5×10~8 CFU),while the 1×10~8 CFU group showed 40% mortality. Bacteria re-isolated from deceased mouse organs were PCR-confirmed as identical to XF-1.更多还原