Prevalence and Drug-susceptibility of Enterohemorrhagic Escherichia coli O157 in Cattle during the Summer

Abstract

In cattle, prevalence of Escherichia coli O157 (O157) increases during the summer. To investigate this prevalence, we isolated 0157 from gastrointestinal contents in summertime. The bacteria were isolated from 22 of 55 (40.0%) animals. Six animals (27.3%) tested 0157-positive for rectal contents only, 10 animals for rumen contents only, and six animals for both. Thus prevalence was especially high in rumen contents. The average number of O157 bacteria in rectal contents was 44CFU/g. The maximum number was 3.8-10⁴CFU/g, but values were<10CFU/g in more than 40% of the samples. Investigation of drug-susceptibility in all 28 isolates showed that 15 were resistant to SM, 11 to ABPC, 4 to CEZ, 4 to FOM, 3 to NA, and 2 to KM. Significantly 4 isolates (14.3%) resisted FOM, which is commonly used to treat human O157 infection.