Absence of High-Level Vancomycin Resistance
Enterococci isolated from packaging areas of meat-processing facilities that produce ready-to-eat meat products were examined for high-level vancomycin resistance. A total of 406 enterococci isolates from the plants' packaging areas were examined for vancomycin resistance. High-level vancomycin resistance was not demonstrated in any enterococci isolated from 12 meat-processing plants.

Since 1989, vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens. In the United States, the prevalence of VRE in hospitals has increased from 0.3% in 1989 to 11%-13% by 1996 in patients other than those in intensive care units. Currently in the United States, more than half of all clinical isolates of Enterococcus faecium are not treatable with vancomycin. Another concern is that, as enterococci are found in the gastrointestinal tract of humans and animals, they may serve as a reservoir of glycopeptide resistance genes that may be transferred to other organisms such as methicillin-resistant Staphylococcus aureus and S. epidermidis.

The source of VRE is not known, although two potential reservoirs for these organisms are hospitals and food animals fed growth promoters, such as avoparcin. Padiglione et al. found that human fecal colonization with VRE is uncommon in Australia, despite the relatively high level of consumption of avoparcin by industry (10,000 kg/year). In Europe, there have been numerous reports of VRE isolated from food animals and food products. In the United States, Knudtson and Hartman studied the prevalence of antimicrobial resistance in enterococci from water, pork, and clinical isolates. In their studies, no VRE was detected from pork carcasses or fresh or spoiled pork products. Also in the United States, Coque et al. and Thal et al. studied enterococci from animal sources and did not recover VRE from the samples examined.

Avoparcin was licensed in Europe in 1975 and subsequently banned throughout the European Union in 1997. In Australia, the per capita consumption of avoparcin by Australian agriculture is one of the highest in the world, while in the United States avoparcin has never been licensed for animal feed. The incidence of VRE infections in European countries is relatively low compared with the high, increasing rate in the United States, indicating that clinical use of vancomycin may be the reason for differences observed between the two populations.

The food chain has been proposed as a suspected source for dissemination of VRE to the human population. Should this be the case, one possible source is plants that produce ready-to-eat foods. Enterococci can be found in the environment of food-processing facilities, including those producing ready-to-eat meat and poultry products, but the incidence of vancomycin resistance among enterococci from these facilities is not known. We investigated the presence of VRE in 12 meat-processing plants in 8 U.S. states.