Use of streptogramin growth promoters in poultry and isolation of streptogramin-resistant Enterococcus faecium from humans

Background. Virginiamycin use in poultry selects for Enterococcus faecium with cross-resistance to quinupristin-dalfopristin, a drug for vancomycin-resistant E. faecium in humans. We conducted an epidemiologic study of poultry exposures as risk factors for human carriage of quinupristin-dalfopristin-resistant E. faecium. Methods. Rectal or fecal samples for E. faecium testing were obtained from 567 newly admitted hospital patients and 100 healthy vegetarians. Participants were interviewed regarding poultry exposure. Retail poultry washes (160 conventional and 26 antibiotic free) were also tested for the presence of E. faecium. Constitutive and inducible quinupristin-dalfopristin resistance were assessed in E. faecium isolates, and resistance genes were identified by polymerase chain reaction. Results. E. faecium was isolated from 105 patients, 65 vegetarians, and 77 conventional and 23 antibiotic-free poultry washes. Constitutive quinupristin-dalfopristin resistance was absent in human E. faecium, but 56% of conventional poultry isolates were quinupristin-dalfopristin resistant. Inducible quinupristin-dalfopristin resistance was more common in samples from patients than in those from vegetarians and in washes of conventional than antibiotic-free poultry. Higher poultry consumption was associated with inducible quinupristin-dalfopristin resistance. vatE was present in 38% of E. faecium isolates from patients and none from vegetarians. Touching raw poultry was associated with the presence of vatE. Conclusions. Poultry exposure is associated with a quinupristin-dalfopristin resistance gene and inducible quinupristin-dalfopristin resistance in human fecal E. faecium. The continued use of virginiamycin may increase the potential for streptogramin-resistant E. faecium infection in humans.