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Inducible, transferable resistance to vancomycin in Enterococcus faecalis A256
D M Shlaes1, A Bouvet, C Devine
1Département de Microbiologie Médicale, Faculté de Médecine, Université Pierre et Marie Curie, Paris, France.
Abstract:
A strain of Enterococcus faecalis (A256) was isolated from the urine of a patient with urinary sepsis and was found to exhibit susceptibilities (micrograms per milliliter) to various glycopeptides as follows: vancomycin, 256; teicoplanin, 16; 62208, 512; 62211, 4; and 62476, 16. As judged by growth rates before and after exposure to sub-MICs of glycopeptides, vancomycin and 62476 induced self-resistance, 62208 and 62211 induced slight self-resistance, and teicoplanin did not induce self-resistance. Vancomycin induced cross-resistance to all other glycopeptides tested, as judged both in growth experiments and by direct measurement of inhibition of peptidoglycan synthesis in cells exposed to sub-MICs of vancomycin. Thus, the spectra of activity of the glycopeptides were not correlated with their patterns of induction. There was a correlation between the increased synthesis of a 39-kilodalton (kDa) protein located in the cytoplasmic membrane and the induction of resistance. Protoplasts of A256 were susceptible to inhibition of peptidoglycan synthesis by vancomycin at levels similar to those for susceptible strains. Vancomycin resistance was transferable on filters from the parent strain to E. faecalis JH2-2 at a frequency of about 10(-7), and the 39-kDa protein was also inducible by glycopeptides in these transconjugants. We conclude that A256 is resistant to glycopeptides by virtue of the synthesis of a 39-kDa cytoplasmic membrane protein, that this protein is probably involved in preventing access of the glycopeptides to their peptidoglycan targets, and that this resistance is transferable, probably by conjugation.
Insights
A strain of Enterococcus faecalis developed resistance to glycopeptides, including vancomycin. This resistance is linked to a specific 39-kDa protein and is transferable between bacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Pharmacology
Background:
- Enterococcus faecalis is a common cause of urinary tract infections.
- Glycopeptides, such as vancomycin, are critical antibiotics for treating infections caused by Gram-positive bacteria.
- Emergence of antibiotic resistance in E. faecalis poses a significant public health threat.
Purpose of the Study:
- To investigate the mechanism of glycopeptide resistance in a clinical isolate of Enterococcus faecalis (A256).
- To determine the role of specific proteins in mediating this resistance.
- To assess the transferability of glycopeptide resistance.
Main Methods:
- Isolation and susceptibility testing of Enterococcus faecalis A256 to various glycopeptides.
- Growth rate analysis before and after exposure to sub-inhibitory concentrations (sub-MICs) of glycopeptides.
- Measurement of peptidoglycan synthesis inhibition.
- Analysis of protein synthesis, specifically a 39-kilodalton (kDa) protein.
- Bacterial conjugation experiments to assess resistance transfer.
Main Results:
- Enterococcus faecalis A256 exhibited high-level resistance to vancomycin and other glycopeptides.
- Exposure to sub-MICs of vancomycin induced self-resistance and cross-resistance to other glycopeptides.
- A 39-kDa protein in the cytoplasmic membrane was found to be upregulated upon glycopeptide exposure.
- Vancomycin resistance was transferable to susceptible E. faecalis strains via conjugation.
- The 39-kDa protein was also inducible in transconjugants.
Conclusions:
- The glycopeptide resistance in E. faecalis A256 is mediated by the inducible synthesis of a 39-kDa cytoplasmic membrane protein.
- This protein likely hinders glycopeptide access to their peptidoglycan targets.
- The resistance mechanism is transferable, suggesting a potential for rapid dissemination in clinical settings.