Inter-batch contamination and potential sources of vancomycin-resistant Enterococcus faecium on broiler farms

Abstract

1. Vancomycin-resistant Enterococcus faecium (VRE_fm) has recently spread among Swedish broiler farms. The objectives were to investigate VRE_fm persistence within barns between flocks, and to determine whether day-old chicks, feed or forklift trucks used for loading crates could be identified as a means of transmission.

2. Faeces were collected for selective culture from 12 farms (9 culture-positive, 3 culture-negative as determined by prior monitoring), and samples were collected from the barn environment before and after cleaning and disinfection, from forklift tyres, hatcheries and feed.

3. VRE_fm was isolated only from previously known VRE_fm-positive farms. The proportions of culture-positive environmental samples were 75% (9 out of 9 farms) prior to and 31% (7 out of 9 farms) after cleaning/disinfection. Five out of 6 samples from forklift tyres were culture-positive. No VRE_fm were isolated from feed or hatcheries. The majority of 27 vanA gene positive isolates showed similar banding patterns by SmaI restriction digestion and pulse-field gel electrophoresis. No consistent differences were observed regarding management between VRE_fm-positive and negative farms.

4. We conclude that VRE_fm contaminates barns and remains present between flocks. Forklift trucks are one possible means of transmission between farms.

Acknowledgements

This study was supported by The Swedish Farmers' Foundation for Agricultural Research (SLF). The authors wish to thank the farmers for obtaining the samples, and Verena Rehbinder is acknowledged for technical assistance.