牛源溶血性曼氏杆菌新疆株的分离鉴定和生物学特性

Isolation,Identification and Biological Characteristics of Mannheimia hacmolytica Strains from Bovine Sources in Xinjiang

为探究新疆维吾尔自治区北疆3个奶牛养殖场和2个肉牛养殖场中犊牛死亡的原因,本试验采集有肺炎症状死亡牛的肺脏和有呼吸道症状牛的鼻拭子样品,进行细菌分离培养、生化鉴定、血清型和毒力基因PCR检测、药敏特性分析和小鼠毒力测定。结果显示:从20份样品中分离到4株溶血性曼氏杆菌,血清型A1型1株、A6型3株;4株分离菌株均能扩增出lktC、plpE、gs60、gcp和tbpB五种毒力基因;4株分离菌株均对恩诺沙星、氧氟沙星、呋喃唑酮、新霉素、青霉素和庆大霉素耐药,对四环素、头孢拉啶和头孢唑啉敏感。4株分离菌株对小鼠的半数致死量由低到高分别为TK-TC1株=2.7×10^(7)CFU/mL、TK-YL3株=8.5×10^(7)CFU/mL、TK-YL4株=5.4×10^(8)CFU/mL和TK-YL7株=2.1×10^(9)CFU/mL,其中TK-TC1株毒力最强。本试验可为牛场由溶血性曼氏杆菌引起的呼吸道疾病的治疗提供参考。

To investigate the causes of calf mortality in three dairy farms and two beef cattle farms in northern Xinjiang,China,lung tissues from deceased cattle with pneumonia symptoms and nasal swabs from cattle with respiratory symptoms were collected.Bacterial isolation,biochemical identification,PCR detection of serotyping and virulence genes,antibiotic susceptibility analysis,and mouse virulence test were conducted.The results showed that four strains of Mannheimia hacmolytica were isolated from 20 samples,with serotypes A1(1 strain)and A6(3 strains).All four isolated strains carried five virulence genes,including lktC,plpE,gs 60,gcp and tbpB.They exhibited resistance to enrofloxacin,ofloxacin,furazolidone,neomycin,penicillin,and gentamicin,while being sensitive to tetracycline,cefradine,and cefazolin.The median lethal dose(LD 50)to mice of the four strains from low to high were TK-TC1=2.7×10^(7)CFU/mL,TK-YL3=8.5×10^(7)CFU/mL,TK-YL4=5.4×10^(8)CFU/mL,and TK-YL7=2.1×10^(9)CFU/mL,with TK-TC1 being the most virulent.This study provides valuable insights for the treatment of respiratory diseases caused by Mannheimia hacmolytica in cattle farms.