|VAN HOANG, KY - University Of Tennessee|
|STERN, NORMAN - Former ARS Employee|
|LIN, JUN - University Of Tennessee|
Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2011
Publication Date: N/A
Interpretive Summary: Bacteriocins are small antimicrobial peptides produced by lactic acid bacteria that are used as probiotic treatments to improve animal and human gastrointestinal health. The bacteriocin E760 was originally isolated from lactic acid bacteria during collaborations with ARS scientists and Russian investigators during an ARS Office of International Research Programs sponsored research project. Bacteriocin E760 can effectively reduce numbers of the food-borne human bacterial pathogen Campylobacter jejuni in chickens when added to feed or water during experimental poultry production. Campylobacter jejuni was grown in the lab in the presence of the bacteriocin E760 to select for mutant bacteria that are resistant to the killing effect of the antimicrobial peptide. Following selection in the lab, bacteriocin-resistant campylobacters were fed to chickens and the stability of the resistant bacteria in the chicken gastrointestinal system was monitored for continued resistance. It was determined that resistance to the bacteriocin was low and resistant numbers of Campylobacters were not maintained at high levels in the chicken gastrointestinal system. Consequently, bacteriocins remain a good potential alternative to antibiotics for use during poultry production to prevent human food-borne disease caused by campylobacters from chickens.
Technical Abstract: Aims: Several bacteriocins (BCNs) identified from chicken commensal bacteria dramatically reduced Campylobacter colonization in poultry and aredirected toward on farm control of this important food-borne human pathogen. BCN resistance in C. jejuni is very difficult to develop in vitro. In this study, in vivo development and stability of BCN resistance in Campylobacter was examined. Methods and Results: Chickens infected with C. jejuni were treated with BCN E760 at the dose of 5 mg/kg body weight/day via oral gavages for three consecutive days, which selected for BCN-resistant (BCNr10 ) Campylobacter mutants in the treated birds. However, all the in vivo-selected mutants only displayed low-levels of resistance to BCN (MIC = 2-8 mg/L) when compared to the parent strain (MIC = 0.5 mg/L). Inactivation of CmeABC efflux pump of the BCNr 12 mutants led to increased susceptibility to BCN (8-32 fold MIC reduction). Three different BCNr Campylobacter strains (in vitro- or in vivo-derived) were examined for the stability of BCN resistance using both in vitro and in vivo systems. The low-level of BCN resistance in these strains was not stable in vitro or in vivo in the absence of BCN selection pressure. Conclusions: Usage of BCN E760 only selected a low-level of BCNr C. jejuni mutants in vivo and the low-level BCN resistance was not stable in vitro or in vivo. Significance and Impact of the Study: The study provides helpful information for risk assessment of the future practical application of the anti-Campylobacter BCNs in animals.