一株致猪胃溃疡大肠杆菌的分离鉴定

四川某猪场暴发保育猪与育肥猪水样腹泻,病理剖解可见胃黏膜大面积脱落、胃溃疡等症状,采集病死猪扁桃体与肠系膜淋巴结进行病毒检测;以肠内容物做寄生虫卵检测;选取其中一代表病例做细菌分离,经小鼠致死试验、仔猪回归试验确定病原菌,并对病原菌进行了形态学观察、生化鉴定、16SrDNA序列分析及药敏试验。结果显示,猪瘟病毒、伪狂犬病病毒等的检测结果为阴性;无寄生虫感染;从十二指肠内容物中分离到1株疑似致病性大肠杆菌,并命名为SCDC-1。用SCDC-1株人工感染健康仔猪成功复制出水样腹泻、胃溃疡病例。对SCDC-1株进行16SrDNA克隆测序,并与GenBank中的8株肠杆菌科和4株巴氏杆菌科菌株的16S基因进行同源性分析,发现SCDC-1株与大肠杆菌16S基因的相似性高达99.5%～99.9%。药敏试验结果显示,该病原菌仅对头孢曲松钠、头孢吡肟、丁胺卡那霉素敏感。试验结果证实,引起此次保育猪与育肥猪胃溃疡的主要病原为致病性大肠杆菌。

Isolation and identification of enteropathogenic Escherichia coli from swine with gastric ulcer

An infectious disease occurred in a pig farm in Sichuan Province,which was characterized by water-like diarrhea,gastric mucosa shedding and gastric ulcer. To identify the reason,one representative sample was selected for pathogen detection,mesenteric lymph nodes were collected for virus detection,and intestinal contents and liver were collected for the separation of parasites and bacteria. In result,no viruses and parasites were dected but one bacterial strain(SCDC-1) was isolated from the intestinal contents,and confirmed by pathogen purification, mice pathogenic experiment, pig return experiment,and biochemical test. The 16S rDNA sequence of SCDC1 was found to be consistent with that of eight strains of Enterobacteraceae and four strains of Pasteurella deposited in the GenBank. Homology analysis revealed that the identity of 16S rDNA sequence between isolated strain and four E.coli strains were from 99.5% to 99.9%. The pig return experiment proved that the artificially infection can causes the same disease symptoms as before. In addition,sensitive drug screen revealed that the SCDS strain was sensitive to ceftriaxone sodium,cefepime and amikacin. In conclusion,the main pathogen of pig gastric ulcer in this case is Escherichia coli.