Survival of Enterococcus faecalis OG1RF:pCF10 in poultry and cattle feed: vector competence of the red flour beetle, Tribolium castaneum (Herbst).

Laboratory experiments were designed to determine the survival of Enterococcus faecalis OG1RF:pCF10 in poultry and cattle feed and its acquisition and transmission by adults of the red flour beetle, Tribolium castaneum (Herbst), to sterile feed. Adult T. castaneum beetles were introduced into poultry and cattle feed inoculated with E. faecalis OG1RF:pCF10 and incubated at 28 degrees C with 65% relative humidity for 7 days in a growth chamber. E. faecalis survived in both poultry and cattle feed during the 7-day test period. There was a logarithmic decrease in E. faecalis concentration in poultry and cattle feed and in and on the insects. E. faecalis persisted on the surface and within T. castaneum adults for 7 days when adults were released on E. faecalis-inoculated poultry feed and for only 5 days on E. faecalis-inoculated cattle feed. The concentration of E. faecalis decreased more slowly on poultry feed than on cattle feed, and this may explain why adult T. castaneum insects were more successful in acquiring and transferring E. faecalis from inoculated poultry feed to sterile poultry feed during the 7-day test period. However, T. castaneum adults reared on inoculated cattle feed were unable to contaminate sterile cattle feed on day 7. To our knowledge, this is the first report documenting T. castaneum to successfully acquire antibiotic-resistant enterococci from animal feed and transfer them to sterile feed. Management of T. castaneum through effective integrated pest management program is therefore important to prevent the spread of antibiotic-resistant and virulent enterococci in animal feed and feed manufacturing environments.