Human infections caused by glycopeptide-resistant Enterococcus spp: are they a zoonosis?

Abstract

Following the detection of glycopeptide-resistant enterococci (GRE) in 1986 and their subsequent global dissemination during the 1990s, many studies have attempted to identify the reservoirs and lines of resistance transmission as a basis for intervention. The eradication of reservoirs and the prevention of GRE spread is of major importance for two reasons: (i) the emergence of high-level glycopeptide resistance in invasive enterococcal clinical isolates that are already multiresistant, has left clinicians with therapeutic options that are only at the experimental stage; and (ii) the resistance genes may spread to more virulent bacterial species such as Staphylococcus aureus, Streptococcus pneumoniae and Clostridium difficile. VanA-type strains, resistant to high levels of both vancomycin and teicoplanin, are the most commonly encountered enterococci with acquired glycopeptide resistance in humans. A widespread VanA-type GRE reservoir was detected early in farm animals that were exposed to the glycopeptide growth-promoter avoparcin. Numerous studies have provided indirect evidence for the transfer of VanA-type GRE and their resistance determinants from animal reservoirs to humans. The data collected have expanded our understanding of the promiscuous nature of antibiotic resistance, and have provided the groundwork for logical decision-making with the objective of deterring the dissemination of resistant bacteria and of their resistance genes.

Persistence of Animal and Human Glycopeptide-Resistant Enterococci on Two Norwegian Poultry Farms Formerly Exposed to Avoparcin Is Associated with a Widespread Plasmid-Mediated vanA Element within a Polyclonal Enterococcus faecium Population

“…Studies of VanA-type GREF have mainly demonstrated plasmid localization for Tn1546, as reviewed by Sundsfjord et al (46). Our hybridization analyses of ClaI-restricted plasmid DNA from each GREF type confirmed the presence of single vanA clusters within diverse RFLPs.…”

“…Several lines of evidence have supported a link between the use of the glycopeptide antibiotic avoparcin as a growth-promoting agent in livestock and the occurrence of GRE in the community (1,7,31,33,43,46,52,55). Thus, the use of avoparcin was abandoned in Norway and Denmark in 1995, in Germany in 1996, and in all remaining European Union countries in 1997 in order to reduce human exposure to animal GRE.…”

VanA-Type Enterococci from Humans, Animals, and Food: Species Distribution, Population Structure, Tn 1546 Typing and Location, and Virulence Determinants

“…Glycopeptide-resistant enterococci (GRE), which have emerged as nosocomial pathogens in the past 10 to 15 years (7), are a global problem despite major epidemiological differences between Europe and the United States. A high frequency of GRE has been reported in hospitals in the United States, whereas extremely low frequencies have been reported in the community, in animals, and in food of animal origin (7,12,29,39,51).…”

Multiple Antibiotic Resistance Gene Transfer from Animal to Human Enterococci in the Digestive Tract of Gnotobiotic Mice

“…The acquisition and spread of glycopeptide-resistant enterococci (GRE) is a global problem, although the selective pressure that has led to dissemination differs between geographical areas (19). In the United States, where antibiotics which represent high-level risk factors for colonization or infection by GRE are extensively prescribed, such strains are isolated from hospitalized patients but not from community-based volunteers without hospital exposure or from the environment or animals (4,10).…”