prevalence of verotoxin-producing escherichia coli (vtec) in a survey of dairy cattle in najaf, iraq

background and objectives: dairy cattle have been implicated as principal reservoir of verotoxin-producing escherichia coli (vtec), with undercooked ground beef and raw milk being the major vehicles of food borne outbreaks. vtec has been implicated as an etiological agent of individual cases and outbreaks in developed countries. this study was designed to determine the prevalence of vetec in diarrheic dairy calves up to 20 days of age in najaf, iraq. materials and methods: 326 fecal samples from diarrheic calves were collected for isolation of escherichia coli o157:h7 and non-o157 vtec isolates. non-sorbitol fermentation, enterohemolysin phenotype, and slide agglutination with antisera were used for screening and detection of these serotypes. results: nineteen (5.8%) non-sorbitol fermenting and 3 (0.9%) enterohemolysin-producing e. coli were obtained. only 9 were agglutinated with available antisera and none of them belonged to the o157:h7 serotype. three were found to be verotoxin positive on vero cell monolayers. these included serotype o111 (2 isolates) and serotype o128 (1 isolate). all three vtec isolates were resistant to ampicillin and streptomycin. two exhibited adherence phenotype on hep-2 cells. conclusion: e. coli o157:h7 serotype is not prevalent in diarrheic dairy calves, and vtec is not a frequent cause of diarrhea in calves in najaf/ iraq.