Genetic linkage between erm(B) and vanA in Enterococcus hirae of poultry origin.
Vancomycin-resistant enterococci (VRE) have frequently been isolated from Norwegian poultry production following the prohibition of the glycopeptide growth promoter avoparcin since 1995. In the present study, a close genetic linkage between the vanA and erm(B) determinants in an Enterococcus hirae isolate of poultry origin is demonstrated, a result that indicates a mechanism for co-selection and maintenance of vancomycin resistance in absence of selective pressure from avoparcin. A total of 36 vanA-positive enterococci of poultry origin, also phenotypically resistant to erythromycin and/or tetracycline, were analyzed by PCR for identification of erm and tet resistance determinants. An E. hirae isolate harbored erm(B) and tet(K), and in this isolate vanA and erm(B) were located on a BamHI fragment of an approximately 50-kb plasmid. Approximately 3 kb of this fragment was amplified by PCR with vanA and erm(B) primers. Sequence analysis of the region between erm(B) and vanZ of Tn1546 showed a truncated IS1216V inserted downstream of the erm(B) stop codon, aligned with a conserved copy of the 3'-inverted terminal repeat of Tn1546. Mating experiments with the E. hirae isolate as donor and E. faecalis JH2-2 as recipient did not result in any transconjugants, indicating that the vanA/erm(B)-carrying plasmid was nonconjugative under the given experimental conditions.
Borgen
Katrine
K
Department of Pharmacology, Microbiology and Food Hygiene, The Norwegian School of Veterinary Science. N-0033 Oslo, Norway.
Sørum
Marit
M
Wasteson
Yngvild
Y
Kruse
Hilde
H
Oppegaard
Hanne
H
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D019729:Carbon-Oxygen Ligases / Q000235:genetics*; D003227:Conjugation, Genetic; D003718:Denmark; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000187:drug effects / Q000235:genetics*; D004917:Erythromycin / Q000494:pharmacology; D008040:Genetic Linkage; D017403:In Situ Hybridization; D008780:Methyltransferases / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D011200:Poultry / Q000382:microbiology*; D013753:Tetracycline Resistance
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C071437:VanA ligase, Bacteria; D004917:Erythromycin; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase; D019729:Carbon-Oxygen Ligases