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Tn924, a chromosome-borne transposon encoding high-level gentamicin resistance in Enterococcus faecalis
L A Thal1, J W Chow, D B Clewell
1Department of Medicine, William Beaumont Hospital, Royal Oak, MI 48073.
Antimicrobial Agents and Chemotherapy
|May 1, 1994
Summary
High-level gentamicin resistance in Enterococcus faecalis SF350 was linked to a novel transposable element, Tn924. This genetic element, located on the chromosome, could be mobilized by a conjugative plasmid, aiding its spread.
Area of Science:
- Microbiology
- Genetics
- Antimicrobial Resistance
Background:
- Enterococcus faecalis is a significant opportunistic pathogen.
- High-level gentamicin resistance (HLGR) in enterococci poses challenges for treatment.
- Understanding the genetic basis of HLGR is crucial for infection control.
Purpose of the Study:
- To characterize the genetic determinant of high-level gentamicin resistance in Enterococcus faecalis SF350.
- To investigate the location and mobility of the gentamicin resistance gene.
Main Methods:
- Bacterial isolation and characterization of Enterococcus faecalis SF350.
- Determination of minimum inhibitory concentration (MIC) for gentamicin.
- Plasmid conjugation experiments.
- Genetic and physical mapping of the resistance determinant.
Main Results:
- Enterococcus faecalis SF350 exhibited high-level gentamicin resistance (MIC > 2,000 µg/ml).
- The gentamicin resistance determinant was located on the bacterial chromosome.
- A coresident conjugative plasmid, pYN120, was capable of mobilizing the resistance determinant.
- Genetic analysis identified a 27-kb transposable element, designated Tn924, carrying the resistance gene.
Conclusions:
- The gentamicin resistance in E. faecalis SF350 is mediated by a chromosomal element, Tn924.
- Tn924 is a mobilizable transposable element, suggesting potential for dissemination.
- This finding contributes to understanding the genetic mechanisms of antimicrobial resistance in Enterococcus species.