title: A longitudinal study to assess the persistence of vancomycin-resistant Enterococcus faecium (VREF) on an intensive broiler farm in the United Kingdom.
abstract: 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.
authors.affiliation: Danish Technical University, National Food Institute, Unit for Antimicrobial Resistance, Bülowsvej, Copenhagen V, Denmark.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Garcia-Migura
authors.forename: Ernesto
authors.initials: E
authors.lastname: Liebana
authors.forename: Lars Bogø
authors.initials: LB
authors.lastname: Jensen
authors.forename: Simon
authors.initials: S
authors.lastname: Barnes
authors.forename: Eve
authors.initials: E
authors.lastname: Pleydell
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002645:Chickens; D004203:Disinfection / Q000379:methods; D016984:Enterococcus faecium / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D004777:Environment; D005243:Feces / Q000382:microbiology; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology / Q000382:microbiology; D006799:Housing, Animal; D008137:Longitudinal Studies; D011201:Poultry Diseases / Q000453:epidemiology* / Q000382:microbiology; D006113:United Kingdom / Q000453:epidemiology; D020713:Vancomycin Resistance / Q000235:genetics*