García D, Cavazza M E, Botero L, Gorziglia M, Urbina G, Liprandi F, Esparza J
Vet Microbiol. 1987 Jan;13(1):47-56. doi: 10.1016/0378-1135(87)90097-6.
The aetiology of neonatal porcine diarrhoea was studied in 15 different herds located in the north-western region of Venezuela. Of 56 strains of Escherichia coli analyzed, 16 (28.6%) were shown to produce heat-stable (STa) enterotoxin, as detected by infant mouse assay. Only four of these STa+ isolates also possessed the K88 pilus antigen, two were 987P+ and none possessed the K99 antigen, leaving 10 STa+ samples in which no pilus antigen was identified. Among the 40 STa negative samples were six K88+ specimens, one K99+, four 987P+, one which reacted as K88+ + K99+ and one K88+ + 987P+. Considering as pathogenic any strain showing at least one of the characters studied, pathogenic E. coli were detected with an overall frequency of 42.9%, being more prevalent during the second week of life. An electrophoretic analysis of the plasmid content of the field isolates of E. coli, revealed the presence of numerous species of extrachromosomal DNA, although no direction association could be made between a particular plasmid and any of the pathogenic characteristics identified. Results of Southern blot analysis indicate that the STa enterotoxin was preferentially encoded within an endemic plasmid of 4.9 Md. Other plasmids present in the E. coli isolates could be related to antibiotic resistance. With the exception of one strain, all E. coli isolates were resistant to more than one of the nine drugs tested; multiresistant E. coli were frequently isolated, including four strains which were resistant to seven antibiotics.
对位于委内瑞拉西北部地区的15个不同猪群的新生仔猪腹泻病因进行了研究。在分析的56株大肠杆菌中，通过幼鼠试验检测发现，有16株（28.6%）产生热稳定（STa）肠毒素。这些产STa的分离株中只有4株同时具有K88菌毛抗原，2株具有987P菌毛抗原，无一株具有K99抗原，其余10株产STa样本未鉴定出菌毛抗原。在40株STa阴性样本中，有6株K88阳性、1株K99阳性、4株987P阳性、1株同时反应为K88 + K99阳性和1株K88 + 987P阳性。将表现出所研究的至少一种特征的任何菌株视为致病菌，检测到致病性大肠杆菌的总体频率为42.9%，在仔猪出生后第二周更为普遍。对大肠杆菌田间分离株的质粒含量进行电泳分析，结果显示存在多种染色体外DNA，但无法确定特定质粒与所鉴定的任何致病特征之间存在直接关联。Southern印迹分析结果表明，STa肠毒素优先由一个4.9 Md的地方性质粒编码。大肠杆菌分离株中存在的其他质粒可能与抗生素耐药性有关。除一株外，所有大肠杆菌分离株对所测试的9种药物中的一种以上耐药；经常分离到多重耐药的大肠杆菌，其中4株对7种抗生素耐药。
