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Seven years after the ban of avoparcin, VREF could still be isolated within sectors of the UK broiler industry. The aim of this study was to assess whether there is a carryover of VREF between consecutive flocks of birds, to conduct a preliminary investigation of possible routes of entry of VREF into broiler houses and to follow the dynamics of VREF shed by growing birds. A series of nine visits were made to two of six houses on a conventional broiler farm. A total of 343 vanA VREF were recovered from environmental (95/843) and faecal (248/416) samples. Significant differences were observed in the carryover of VREF between pre- and postcohort postcleaning and disinfection visits (RR 0.57, P=0.006). Ninety-nine percent of the VREF isolates were resistant to more than five antimicrobials, with 42 isolates (n=49) positive for erm(B) and 32 (n=40) for vat(E). Pulsed field gel electrophoresis (PFGE) typing identified 50 PFGE types within 15 different PFGE clusters of 90% similarity, demonstrating a high level of genetic diversity within VREF populations from epidemiologically related broiler flocks and broiler houses. Further characterization of Tn1546 from different clones showed a low diversity of Tn-types, suggesting horizontal transfer of resistance determinants between different genetic clones. Thus, this study does not only show the persistence of VREF but also of multi-drug resistant lineages of VREF.
Original languageEnglish
JournalF E M S Microbiology Letters
Issue number2
Pages (from-to)319-325
StatePublished - 2007
CitationsWeb of Science® Times Cited: 15


  • antimicrobial resistance, vancomycin, molecular characterization
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ID: 3678163