title: Distribution of streptogramin resistance determinants among Enterococcus faecium from a poultry production environment of the USA.
abstract: OBJECTIVE
  The impact of agricultural use of antimicrobials on the present and future efficacy of therapeutic drugs in human medicine is a growing public concern. Quinupristin/dalfopristin has been approved to treat human disease caused by vancomycin-resistant Enterococcus faecium and is related to virginiamycin, a streptogramin complex that has long been used in USA agriculture poultry production.
  
  
  METHODS
  Streptogramin-resistant isolates of E. faecium from poultry production environments on the eastern seaboard were recovered without selection for streptogramin resistance and examined using ribotyping to evaluate clonal bias. Colony PCR screening for the previously described streptogramin resistance determinants erm(A), erm(B), msr(C), vgb(A), vat(D) and vat(E) was performed to determine the prevalence of streptogramin resistance mechanisms from these environments.
  
  
  RESULTS
  The collection of E. faecium isolates was unevenly distributed among 28 ribogroups and did not cluster geographically. The most prevalent ribogroups was composed of isolates that possessed diverse antimicrobial resistance profiles. Of the 127 isolates examined, 63% were resistant to quinupristin/dalfopristin. The resistance determinants erm(A) and erm(B) were observed among 6% and 10%, respectively, of streptogramin-resistant isolates. msr(C) was detected in a single isolate that was resistant to macrolide and lincosamide antimicrobials. The streptogramin B hydrolase vgb(A) and the streptogramin A acetyltransferases genes vat(D) and vat(E) were not detected in any of the E. faecium isolates.
  
  
  CONCLUSIONS
  These results indicate that there is widespread resistance to streptogramin antimicrobials among E. faecium throughout the poultry production region in this study and that the mechanisms of resistance to streptogramin antimicrobials within this population remain largely uncharacterized.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Hayes
authors.forename: David D
authors.initials: DD
authors.lastname: Wagner
authors.forename: Linda L
authors.initials: LL
authors.lastname: English
authors.forename: Lewis E
authors.initials: LE
authors.lastname: Carr
authors.forename: Sam W
authors.initials: SW
authors.lastname: Joseph
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens / Q000382:microbiology*; D003691:Delaware; D024881:Drug Resistance, Bacterial; D016984:Enterococcus faecium / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D004777:Environment; D005516:Food Microbiology; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology / Q000662:veterinary; D008396:Maryland; D011201:Poultry Diseases / Q000382:microbiology; D025361:Streptogramins / Q000494:pharmacology*; D014768:Virginia
chemical_list: D000900:Anti-Bacterial Agents; D025361:Streptogramins