Characterization of monolaurin resistance in Enterococcus faecalis

Area of Science:

• Microbiology
• Food Science
• Antimicrobial Resistance

Background:

• Vancomycin-resistant enterococci (VRE) in farmed animals pose a significant public health risk.
• Understanding monolaurin's antimicrobial mechanisms and resistance is crucial for its use as a food preservative.
• Enterococcus faecalis is a key pathogen of concern in food production environments.

Purpose of the Study:

• To investigate the mechanisms of monolaurin resistance in Enterococcus faecalis.
• To assess the potential of monolaurin as a food preservative by understanding resistance development.

Main Methods:

• Screening of an Enterococcus faecalis AR01/DGVS Tn917 mutant library for monolaurin resistance.
• Identification of the interrupted gene (traB) in resistant mutants.
• Characterization of a resistant mutant (DGRM2) including antibiotic susceptibility, cell autolytic activity, cell surface hydrophobicity, and cell wall structure analysis via transmission electron microscopy.

Main Results:

• Three monolaurin-resistant mutants (DGRM2, DGRM5, DGRM12) were identified, with mutations in the traB gene.
• Mutant DGRM2 exhibited increased resistance to protein synthesis inhibitors but not cell wall-active antibiotics.
• DGRM2 displayed altered cell surface hydrophobicity and increased cell wall thickness, suggesting limited monolaurin diffusion.

Conclusions:

• Monolaurin resistance in Enterococcus faecalis is associated with alterations in cell surface hydrophobicity.
• These changes likely impede monolaurin's access to its cellular targets, reducing its efficacy.
• Findings provide insights into monolaurin resistance mechanisms, informing its application as a food preservative.