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Induction of ermAMR from a clinical strain of Enterococcus faecalis by 16-membered-ring macrolide antibiotics
Abstract:
We cloned the MLSB resistance determinant by PCR from a clinical isolate of Enterococcus faecalis 373, which is induced more strongly by a 16-membered-ring macrolide, tylosin, than by erythromycin. To elucidate the molecular basis of resistance of E. faecalis 373, we analyzed the cloned gene, designated ermAMR, by site-directed mutagenesis and reporter gene assay. Our results showed that an arginine-to-cysteine change in the seventh codon of the putative leader peptide endowed tylosin with resistance inducibility and that TAAA duplication enabled the control region to express the downstream methylase gene at a drastically increased level.
Insights
We identified the MLSB resistance gene in Enterococcus faecalis. A specific mutation in the leader peptide and a duplication in the control region were found to increase resistance to tylosin and other macrolides.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Enterococcus faecalis is a common cause of hospital-acquired infections.
- Macrolide resistance in bacteria is a growing public health concern.
- The MLSB resistance determinant confers resistance to macrolides, lincosamides, and streptogramin B antibiotics.
Purpose of the Study:
- To elucidate the molecular basis of MLSB resistance in a clinical isolate of Enterococcus faecalis.
- To identify the specific genetic elements responsible for resistance induction by tylosin.
Main Methods:
- Polymerase chain reaction (PCR) was used to clone the MLSB resistance determinant.
- Site-directed mutagenesis was employed to analyze the cloned gene (ermAMR).
- Reporter gene assays were performed to assess gene expression levels.
Main Results:
- The cloned gene, ermAMR, was successfully isolated from Enterococcus faecalis 373.
- An arginine-to-cysteine substitution in the seventh codon of the putative leader peptide was crucial for tylosin resistance inducibility.
- A TAAA duplication in the control region led to a significant increase in the expression of the downstream methylase gene.
Conclusions:
- The study identified key genetic alterations conferring macrolide resistance in Enterococcus faecalis.
- The findings provide insights into the mechanisms of antibiotic resistance and can inform strategies to combat resistant infections.