Tylosin resistance in Arcanobacterium pyogenes is encoded by an erm X determinant.
Arcanobacterium pyogenes, a commensal on the mucous membranes of many economically important animal species, is also a pathogen, causing abscesses of the skin, joints, and visceral organs as well as mastitis and abortion. In food animals, A. pyogenes is exposed to antimicrobial agents used for growth promotion, prophylaxis, and therapy, notably tylosin, a macrolide antibiotic used extensively for the prevention of liver abscessation in feedlot cattle in the United States. Of 48 A. pyogenes isolates, 11 (22.9%) exhibited inducible or constitutive resistance to tylosin (MIC of > or = 128 microg/ml). These isolates also exhibited resistance to other macrolide and lincosamide antibiotics, suggesting a macrolide-lincosamide resistance phenotype. Of the 11 resistant isolates, genomic DNA from nine hybridized to an erm(X)-specific probe. Cloning and nucleotide sequencing of the A. pyogenes erm(X) gene indicated that it was >95% similar to erm(X) genes from Corynebacterium and Propionibacterium spp. Eight of the erm(X)-containing A. pyogenes isolates exhibited inducible tylosin resistance, which was consistent with the presence of a putative leader peptide upstream of the erm(X) open reading frame. For at least one A. pyogenes isolate, 98-4277-2, erm(X) was present on a plasmid, pAP2, and was associated with the insertion sequence IS6100. pAP2 also carried genes encoding the repressor-regulated tetracycline efflux system determinant Tet 33. The repA gene from pAP2 was nonfunctional in Escherichia coli and at least one A. pyogenes isolate, suggesting that there may be host-encoded factors required for replication of this plasmid.
Department of Veterinary Science and Microbiology, The University of Arizona, Tucson, Arizona 85721, USA. jost@u.arizona.edu
B Helen
BH
Jost
Adam C
AC
Field
Hien T
HT
Trinh
J Glenn
JG
Songer
Stephen J
SJ
Billington
D000191:Actinomycetaceae / Q000187:drug effects* / Q000235:genetics*; D000193:Actinomycetales Infections / Q000188:drug therapy / Q000382:microbiology; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D001717:Birds; D015139:Blotting, Southern; D002415:Cats; D002417:Cattle; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D004285:Dogs; D024881:Drug Resistance, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D015645:Tylosin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D015645:Tylosin