一株猪丹毒杆菌分离株的致病性与耐药性分析

Pathogenicity and antimicrobial susceptibility analysis of one strain of Erysipelothrix rhusiopathiae

从某猪场病死猪心血、肝、脾等组织分离到1株革兰阳性杆菌,经细菌形态、16S rRNA基因扩增,确定分离菌为猪丹毒杆菌。对分离菌进一步开展了药物敏感性试验、耐药基因的检测、细菌致病性试验及免疫保护性试验。结果发现:分离株对β-内酰胺类、大环内酯类、氟苯尼考高敏,但对氨基糖苷类、四环素、林可霉素、诺氟沙星等耐药;分离株可扩增出氨基糖苷类耐药基因aac C2和四环素耐药基因tetB,但菌株中没有扩增到四环素耐药基因tetA。细菌致病性试验表明该毒株对小鼠的LD50为1.77×10~5cfu/mL。小鼠免疫保护试验结果表明,疫苗G4T10免疫后28 d,以分离株攻毒,对照组全部死亡(5/5),免疫组小鼠攻毒后没有死亡,仅表现为体重减轻,表明现用猪丹毒疫苗能保护小鼠抵抗猪丹毒的致死性攻击。

One strain of Gram positive bacillus was isolated from the blood,liver and spleen tissue of the diseased pig. It was determined to be Erysipelothrix rhusiopathiae based on its morphology and 16 S rRNA gene sequence. The bacterium was further analyzed by antimicrobial susceptibility test,antibiotic resistance gene detection,pathogenicity and the immunity protective test. Antimicrobial susceptibility test showed that the isolate was sensitive to β-lactams,macrolides and chloramphenicols,but resistant to aminoglycosides,lincomycin,tetracycline and norfloxacin. Antibiotic resistance gene detection showed the aminoglycoside resistance gene aac C2 and tetracycline resistance gene tet B could be amplified,but tet A not. Pathogenicity tests showed that the LD50 value of the bacterial strain was 1. 77× 10^5cfu/m L in mice.Mice were challenged after 28-day vaccination with swine erysipelas vaccine G4T10,and the results showed that the immunized mice weren＇t dead with weight loss,but the mortality of the control group was 100%（ 5/5）,indicating that the current swine erysipelas vaccine can protect mice against Erysipelothrix rhusiopathiae infection.