Investigating the adherence factors of <i>Escherichia coli</i> at the bovine recto-anal junction

<i>E. coli</i> strains that produce Shiga toxin cause foodborne illness in humans but colonize cattle asymptomatically. The molecular mechanisms that <i>E. coli</i> uses to adhere to cattle cells are largely unknown. Various strategies are used to control <i>E. coli</i> in livestock and limit the risk of outbreaks. These include vaccinating animals against common <i>E. coli</i> strains and supplementing their feed with probiotics to reduce the carriage of pathogens. No strategy is completely effective, and probiotics often fail to colonize the animals. We sought to clarify the genes required for <i>E. coli</i> adherence in cattle by quantifying the attachment to bovine cells in a diverse set of bacteria. We also isolated nonpathogenic <i>E. coli</i> from healthy cows and showed that a representative isolate could outcompete pathogenic strains in cocultures. We propose that the focused study of these strains and their adherence factors will better inform the design of probiotics and vaccines for livestock.