Author : Pham Hong Ngan

Summary : Rectal fecal samples of diarrheic and nondiarrheic dairy calves (90 each) from 10 selected farms in Hanoi City and Hatay province, Vietnam, were cultured to detect enterotoxigenic Escherichia coli (ETEC) which possess pilus antigen and produce enterotoxin. All calves, less than 30 days old of both sexes, came from unvaccinated and untreated dams. Based on colonial morphology and reaction to biochemical tests, E. coli were isolated from all animals. Slide coaglutination and infant mouse tests revealed that 34.44 percent (31/90) of diarrheic calves had ETEC; only 10 percent (9/90) of nondiarrheic calves harbored these strains. This study only detected ST because bovine isolates of ETEC do not produce LT. Enteroxin-producing E.coli possessing F5 pilus antigen were detected at a higher rate in diarrheic (21 percent) than nondiarrheic claves (7 percent). Similarly, ETEC containing F41 pilus antigen were found in 8.89 percent (8/90) nondiarrheic groups. Only calf each in the diarrheic group and in nondiarrheic group harbored E.coli bearing F6 antigen and producing ST. Three (3.33 percent) diarrheic calves harbored both F5 and F41 producing enterotoxin E.coli. In this study, ETEC containing F5, F41, and F6 pili antigens were found in calves.