Aim: To determine the rate of antibiotic resistance transmission between commensal and pathogenic representatives of the Enterobacteriaceae. Methods and Results: Through the use of a validated in vitro simulation of the porcine ileum, the transmission of antibiotic resistance was detected between commensal Escherichia coli , E. coli O157 and Salmonella spp. Countable transconjugant populations arose readily and, in one example, proved capable of indefinite persistence. Conclusions: Genetic material conferring antibiotic resistance is readily transmissible between members of the Enterobacteriaceae under ileal conditions. Recipient phenotype influences the persistence of multi-resistant transconjugants. Significance and Impact of the Study: The observation that the conjugal transmission of antibiotic resistance is commonplace under ileal conditions impacts primarily on the risk of food contamination by multi-resistant bacteria. The establishment of a multi-resistant transconjugant population as a dominant member of the microflora maintains a genetic reservoir of antimicrobial resistance.