绵羊源溶血性曼氏杆菌A2型的分离鉴定及耐药性分析

Isolation,Identification and Antibiotic Resistance Analysis of A2 Type Mannheimia Haemolytica from Sheep

【目的】新疆某羊场的羊出现精神沉郁、咳嗽气喘、消瘦等症状,为确定此次发病病原。【方法】该羊场共送检4份病羊肺脏,从肺脏中分离培养了一株细菌并对其进行培养特性观察、PCR鉴定、血清型鉴定、药敏试验和动物致病性试验。【结果】结果显示分离出的一株革兰氏阴性菌,其形状及大小疑似溶血性曼氏杆菌;PCR鉴定结果显示为溶血性曼氏杆菌,分离菌株血清型为A2型。该分离菌株对青霉素、头孢唑林、氨苄西林等敏感;在致病性试验中,小鼠在15 h内陆续死亡,说明该菌株具有一定致病力。【结论】该病例致病原为A2型溶血性曼氏杆菌,对青霉素、头孢唑林、氨苄西林等敏感。

【Objective】A farm in Xinjiang reported sheep exhibiting symptoms of lethargy,persistent coughing,audible wheezing,and noticeable weight loss.The research aimed to identify the causative pathogen responsible for these clinical signs.【Methods】Four lung tissue samples from infected sheep were submitted for diagnostic examination.Isolation and culture of a bacterial strain from the samples were performed,followed by the observation of cultural characteristics.A comprehensive analysis was conducted,including polymerase chain reaction(PCR)for bacterial identification,serotype determination,antimicrobial susceptibility testing,and evaluation of pathogenicity using animal models.【Results】A gram-negative bacterium was isolated from the lung samples.Its morphological characteristics strongly suggested it to be Mannheimia haemolytica,commonly referred to as hemolytic Mannheimia spp.Confirmatory PCR analysis identified the bacteria as Mannheimia haemolytica,with the serotype specified as A2.Antimicrobial sensitivity profiling demonstrated that the strain was sensitive to several antibiotics,namely penicillin,cefazolin,and ampicillin.Pathogenicity assays conducted in murine models showed 100%mortality within 15 hours post-infection,asserting the strain’s pathogenic potential.【Conclusion】The offending pathogen responsible for the sheep’s symptoms was pinpointed as serotype A2 Mannheimia haemolytica.The susceptibility of this strain to commonly used antibiotics such as penicillin,cefazolin,and ampicillin provides a therapeutic avenue for effectively managing and curtailing this infectious condition in the sheep population.