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

1. Vancomycin-resistant Enterococcus faecium (VREfm) has recently spread among Swedish broiler farms. The objectives were to investigate VREfm 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. VREfm was isolated only from previously known VREfm-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 VREfm were isolated from feed or hatcheries. The majority of 27 vanA gene positive isolates showed similar banding patterns by SmaI r...