Effect of vancomycin, tylosin, and chlortetracycline on vancomycin-resistant Enterococcus faecium colonization of broiler chickens during grow-out

Authors: Hume, Michael; DONSKEY, CURTIS - Veterans Affairs Medical Center - Cleveland

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2016
Publication Date: 4/1/2017
Citation: Hume, M.E., Donskey, C.J. 2017. Effect of vancomycin, tylosin, and chlortetracycline on vancomycin-resistant Enterococcus faecium colonization of broiler chickens during grow-out. Foodborne Pathogens and Disease. 14(4): 231-237. doi: 10.1089/fpd.2016.2217.

Interpretive Summary: Chickens may serve as reservoirs for the human pathogen vancomycin-resistant Enterococcus (VRE). We examined the effects of the antibiotic vancomycin and two commonly-used antibiotic feed additives on VRE colonization in chickens during grow-out at 6 weeks. Chicks received untreated feed or feed containing vancomycin, chlortetracycline, or tylosin from day-of-hatch to grow-out. At 3 days of age, chicks were inoculated orally with human- or poultry-derived VRE. Intestinal contents were monitored for pH, VRE, organic acids, and bacteria types. Chickens given vancomycin had persistent and high-level colonization with human- and poultry-derived VRE to grow-out in comparison to untreated chickens while chicken given chlortetracycline and tylosin did not. Colonization by the poultry VRE in untreated, chlortetracycline, and tylosin groups persisted throughout the grow-out period with low concentrations present at 6 weeks, whereas the human VRE decreased to an undetectable level by week 6. Vancomycin resulted in significant reductions in organic acids in comparison to untreated chickens, but chlortetracycline and tylosin did not. Intestinal bacteria types of chickens given vancomycin were very different from those of chickens in the other three groups. These results demonstrate that vancomycin, but not chlortetracycline or tylosin, disrupted bacterial and organic acid patterns of chickens and promoted colonization by VRE.

Technical Abstract: Broiler chickens may serve as reservoirs for human colonization by vancomycin-resistant Enterococcus (VRE). We examined the effects of vancomycin and two commonly-used antimicrobial feed additives on VRE colonization in broiler chickens during grow-out. Chicks received unsupplemented feed or feed containing vancomycin, chlortetracycline, or tylosin from day-of-hatch to grow-out at six weeks. At 3 days of age, chicks received by crop gavage 10^7 CFU of a human or poultry VRE isolate. Cecal contents were monitored weekly for pH, VRE, short chain fatty acids (SCFA), and bacterial denaturing gradient gel electrophoresis (DGGE) profiles. Vancomycin promoted persistent and high-level colonization with human- and poultry-derived VRE to grow-out in comparison to controls, while treatment with chlortetracycline and tylosin did not. Colonization by the poultry isolate in control, chlortetracycline, and tylosin groups persisted throughout the grow-out period with low concentrations present at 6 weeks, whereas the human isolate decreased to an undetectable level by week 6. Vancomycin resulted in significant reductions in cecal acetic acid and butyric acid in comparison to controls, but chlortetracycline and tylosin did not. DGGE profiles contained two main clusters with all vancomycin profiles in a smaller cluster and all other profiles in a larger cluster. These results demonstrate that vancomycin, but not chlortetracycline or tylosin, disrupted the indigenous microbiota and SCFA patterns of broiler chickens and promoted colonization by VRE.