Source of Enterococcal Infection in Swedish Broilers

SWEDEN - Researchers have studied environmental contamination by vancomycin-resistant enterococci (VRE) on three broiler farms and found that even a low level of contamination means the infection of all birds over one production cycle.
calendar icon 30 December 2009
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Nilsson of the National Veterinary Institute at Uppsala and colleagues there and at the Swedish University of Agricultural Sciences in the same city have published a paper on their study into the prevalence of vancomycin-resistant enterococci (VRE) in the latest Acta Veterinaria Scandinavica.

In the introduction to their paper, Nilsson and co-authors explain that VRE are a frequent cause of hospital-acquired infection in human patients, and their presence among farm animals is unwanted. Using media supplemented with vancomycin an increase in the proportion of samples from Swedish broilers positive for VRE has been detected. The situation at farm level is largely unknown.

The aims of this study were to obtain baseline knowledge about environmental contamination with VRE in Swedish broiler production and the association between environmental contamination and colonisation of birds.


Environmental samples were taken before, during and after a batch of broilers at three farms. Samples were cultured both qualitatively and semi-quantitatively for VRE. In addition, caecal content from birds in the batch following at each farm was cultured qualitatively for VRE.


The number of samples positive for VRE varied between the farms. Also the amount of VRE in the positive samples and the proportion of caecal samples containing VRE varied between the farms. Still, the temporal changes in environmental contamination followed a similar pattern for all farms.


VRE persist in the compartments even after cleaning and the temporal changes in environmental contamination were similar among farms. There were, however, differences between farms in both the level of contamination and proportion of birds colonised with VRE.

The Uppsala researchers say that their study indicates that even the low degree of VRE contamination seen on one of the farms at the start of the study was sufficient for amplification and spread. As soon as birds are put in to the compartments, they start to become colonised with the persisting VRE.

The proportion of colonised birds and the amount of VRE in the compartments seems to be associated, they say. If the factor(s) causing the differences among farms could be identified, it might be possible to reduce both the risk for colonisation by VRE of the subsequent flock and the risk for spread of VRE via the food chain to humans.


Nilsson O., C. Greko and B. Bengtsson. Environmental contamination by vancomycin resistant enterococci (VRE) in Swedish broiler production. Acta Veterinaria Scandinavica, 51:49 doi:10.1186/1751-0147-51-49

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