A Second Tylosin Resistance Determinant, Erm B, inArcanobacterium pyogenes

Open Access
Publisher Website
Google Scholar
Abstract
Arcanobacterium pyogenes, a common inhabitant of the mucosal surfaces of livestock, is also a pathogen associated with a variety of infections. In livestock,A. pyogenesis exposed to antimicrobial agents used for prophylaxis and therapy, notably tylosin, a macrolide used extensively for the prevention of liver abscessation in feedlot cattle in the United States. Many, but not all, tylosin-resistantA. pyogenesisolates carryerm(X), suggesting the presence of other determinants of tylosin resistance. Oligonucleotide primers designed for conserved regions oferm(B),erm(C), anderm(T) were used to amplify a 404-bp fragment from a tylosin-resistantA. pyogenesisolate, OX-7. DNA sequencing revealed that the PCR product was 100% identical toerm(B) genes, and theerm(B) gene region was cloned inEscherichia coli. TheA. pyogenesErm B determinant had the most DNA identity with an Erm B determinant carried by theClostridium perfringensplasmid pIP402. However, theA. pyogenesdeterminant lacked direct repeat DR1 and contained a deletion in DR2. Flanking theA. pyogenes erm(B) gene were partial and entire genes similar to those found on theEnterococcus faecalismultiresistance plasmid pRE25. This novel architecture suggests that theerm(B) element may have arisen by recombination of two distinct genetic elements. Ten of 32 tylosin-resistant isolates carriederm(B), as determined by DNA hybridization, and all 10 isolates carried a similar element. Insertion of the element was site specific, as PCR and Southern blotting analysis revealed that theerm(B) element was inserted intoorfY, a gene of unknown function. However, in three strains, this insertion resulted in a partial duplication oforfY.

This publication has 28 references indexed in Scilit: