ARS | Publication request: CLEARANCE OF VANCOMYCIN RESISTANT ENTEROCOCCUS FAECIUM ISOLATES FROM AN ANAEROBIC CONTINUOUS-FLOW CULTURE OF CHICKEN MICROFLORA IN THE PRESENCE ANDABSENCE OF SUBTHERAPEUTIC CONCENTRATIONS OF VANCOMYCIN

Submitted to: Society of Microbial Ecology and Disease (SOMED) Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 3, 2001
Publication Date: N/A

Technical Abstract: Experiments were conducted to investigate the bactericidal activity against a vancomycin resistant enterococci (VRE) 7000221, and other enterococci, in an anaerobic continuous-flow fermentation culture of chicken gastrointestinal microorganisms (CCF). When CCF was challenged with 10**7 CFU/ml VRE, the VRE population decreased to an undetectable level after 48 hours and could not be rescued by addition of vancomycin at 4ug/ml. In vitro experiments with vancomycin resistant E. faecium A256, tylosin and virginiamycin resistant E. faecium 3167 and vancomycin resistant E. faecalis 7000802 demonstrated clearance from the CCF in approximately 4 days. Prophylactic treatment of day-old broiler chicks with CCF protected against VRE cecal colonization after VRE challenge as compared to non CCF treated controls. In four replicate experiments, VRE colonization occurred in less than 5% of chicks that were inoculated with CCF prior to challenge with VRE. An additional study was designed to determine the effect of subtherapeutic concentrations of vancomycin on the ability of CCF to clear VRE 7000221. Three experimental groups of CCF were inoculated with 10**7 CFU/ml VRE. Two of these groups were treated with subtherapeutic concentrations of vancomycin, 0.1ug/ml or 0.01ug/ml, respectively, while the third group was not treated with vancomycin. Vancomycin treatment increased the length of time VRE remained in both treated groups from 5 days to 9 days. The results of this study suggest that subtherapeutic doses of 0.1ug/ml or 0.01ug/ml vancomycin were not sufficient to provide a selective advantage to the VRE in the microbial microflora typically inhabiting the chicken ceca.