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A second tylosin resistance determinant, Erm B, in Arcanobacterium pyogenes
B Helen Jost1, Hien T Trinh, J Glenn Songer
1Department of Veterinary Science and Microbiology, The University of Arizona, Tucson, Arizona 85721, USA. jost@u.arizona.edu
Antimicrobial Agents and Chemotherapy
|February 26, 2004
Summary
Tylosin resistance in Arcanobacterium pyogenes is often linked to the erm(B) gene. This study identified a novel erm(B) genetic element in livestock pathogens, suggesting recombination between distinct genetic elements.
Area of Science:
- Veterinary Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Arcanobacterium pyogenes is a livestock pathogen frequently exposed to tylosin, a macrolide antibiotic.
- Tylosin resistance in A. pyogenes is common, with many resistant isolates carrying erm(X), but others suggest additional resistance mechanisms.
- The presence of other tylosin resistance determinants in A. pyogenes warrants further investigation.
Purpose of the Study:
- To identify and characterize novel tylosin resistance genes in Arcanobacterium pyogenes.
- To investigate the genetic basis of tylosin resistance beyond the erm(X) gene.
- To understand the genetic architecture and potential origin of the erm(B) element in A. pyogenes.
Main Methods:
- PCR amplification using primers for erm(B), erm(C), and erm(T) from a tylosin-resistant A. pyogenes isolate (OX-7).
- DNA sequencing of the amplified fragment and comparison to known erm genes.
- Cloning of the erm(B) gene region into Escherichia coli for further analysis.
- DNA hybridization and Southern blotting to detect erm(B) presence and insertion site in other isolates.
Main Results:
- A 404-bp fragment identical to erm(B) was amplified and sequenced from isolate OX-7.
- The A. pyogenes erm(B) determinant showed high identity to erm(B) from Clostridium perfringens but lacked specific repeat regions and had a deletion.
- Genes flanking the erm(B) gene were similar to those on the Enterococcus faecalis multiresistance plasmid pRE25, suggesting a novel genetic element.
- Ten of 32 tylosin-resistant isolates carried erm(B) on a similar element, inserted specifically into the orfY gene, sometimes causing partial duplication.
Conclusions:
- A novel erm(B) genetic element, potentially formed by recombination, is present in tylosin-resistant Arcanobacterium pyogenes.
- This erm(B) element is inserted site-specifically into the orfY gene in resistant isolates.
- The findings contribute to understanding the mechanisms of macrolide resistance in important livestock pathogens.