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A 1.5 Hour Procedure for Identification of Enterococcus Species Directly from Blood Cultures
Published on: February 10, 2011
Enterococcus faecalis Countermeasures Defeat a Virulent Picovirinae Bacteriophage
Julien Lossouarn1, Arnaud Briet2, Elisabeth Moncaut3
1Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France. julien.lossouarn@inra.fr.
Abstract:
Enterococcus faecalis is an opportunistic pathogen that has emerged as a major cause of nosocomial infections worldwide. Many clinical strains are indeed resistant to last resort antibiotics and there is consequently a reawakening of interest in exploiting virulent phages to combat them. However, little is still known about phage receptors and phage resistance mechanisms in enterococci. We made use of a prophageless derivative of the well-known clinical strain E. faecalis V583 to isolate a virulent phage belonging to the Picovirinae subfamily and to the P68 genus that we named Idefix. Interestingly, most isolates of E. faecalis tested-including V583-were resistant to this phage and we investigated more deeply into phage resistance mechanisms. We found that E. faecalis V583 prophage 6 was particularly efficient in resisting Idefix infection thanks to a new abortive infection (Abi) mechanism, which we designated Abiα. It corresponded to the Pfam domain family with unknown function DUF4393 and conferred a typical Abi phenotype by causing a premature lysis of infected E. faecalis. The abiα gene is widespread among prophages of enterococci and other Gram-positive bacteria. Furthermore, we identified two genes involved in the synthesis of the side chains of the surface rhamnopolysaccharide that are important for Idefix adsorption. Interestingly, mutants in these genes arose at a frequency of ~10-4 resistant mutants per generation, conferring a supplemental bacterial line of defense against Idefix.
Insights
Researchers discovered a new phage, Idefix, effective against the opportunistic pathogen Enterococcus faecalis. They identified a novel abortive infection mechanism, Abiα, and rhamnopolysaccharide genes contributing to phage resistance in E. faecalis.
Area of Science:
- Microbiology
- Bacteriology
- Virology
Background:
- Enterococcus faecalis is a significant cause of hospital-acquired infections.
- Antibiotic resistance in E. faecalis necessitates alternative therapeutic strategies.
- Bacteriophages are being re-evaluated as potential agents against resistant bacteria.
Purpose of the Study:
- To isolate and characterize a virulent bacteriophage targeting Enterococcus faecalis.
- To elucidate the mechanisms of phage resistance in E. faecalis.
- To identify bacterial factors involved in phage adsorption and resistance.
Main Methods:
- Isolation of a virulent phage (Idefix) from a clinical E. faecalis strain.
- Investigation of phage resistance mechanisms using a prophageless derivative.
- Identification of abortive infection (Abi) mechanisms and bacterial surface components.
Main Results:
- A novel virulent phage, Idefix, was isolated and belonged to the P68 genus.
- A new abortive infection mechanism, Abiα (Pfam DUF4393), was identified, conferring resistance to Idefix infection.
- Two genes involved in rhamnopolysaccharide synthesis were found crucial for Idefix adsorption, with mutations conferring resistance.
Conclusions:
- Enterococcus faecalis employs multiple strategies to resist phage infection, including abortive infection and alterations in surface polysaccharides.
- The Abiα mechanism represents a novel defense strategy against bacteriophages in Gram-positive bacteria.
- Understanding these resistance mechanisms is critical for developing effective phage-based therapies against E. faecalis infections.
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