Persistent Colonization of Sheep byEscherichia coliO157:H7 and OtherE. coliPathotypes

Publisher Website
Google Scholar
Abstract
Shiga toxin-producingEscherichia coli(STEC) is an important cause of food-borne illness in humans. Ruminants appear to be more frequently colonized by STEC than are other animals, but the reason(s) for this is unknown. We compared the frequency, magnitude, duration, and transmissibility of colonization of sheep byE. coliO157:H7 to that by other pathotypes ofE. coli. Young adult sheep were simultaneously inoculated with a cocktail consisting of two strains ofE. coliO157:H7, two strains of enterotoxigenicE. coli(ETEC), and one strain of enteropathogenicE. coli. Both STEC strains and ETEC 2041 were given at either 107or 1010CFU/strain/animal. The other strains were given only at 1010CFU/strain. We found no consistent differences among pathotypes in the frequency, magnitude, and transmissibility of colonization. However, the STEC strains tended to persist to 2 weeks and 2 months postinoculation more frequently than did the other pathotypes. The tendency for persistence of the STEC strains was apparent following an inoculation dose of either 107or 1010CFU. One of the ETEC strains also persisted when inoculated at 1010CFU. However, in contrast to the STEC strains, it did not persist when inoculated at 107CFU. These results support the hypothesis that STEC is better adapted to persist in the alimentary tracts of sheep than are other pathotypes ofE. coli.