Characterization of Enterococcus faecium mutants resistant to mundticin KS, a class IIa bacteriocin

Area of Science:

• Food microbiology
• Antimicrobial resistance
• Bacteriocin research

Background:

• Bacteriocins are antimicrobial peptides used as food preservatives.
• Emergence of bacteriocin-resistant mutants poses a food safety risk.
• Understanding resistance mechanisms is crucial for effective bacteriocin application.

Purpose of the Study:

• To characterize the physiological traits of Enterococcus faecium mutants resistant to mundticin KS.
• To investigate the impact of bacteriocin resistance on sensitivity to other antimicrobials.
• To elucidate changes in membrane composition associated with bacteriocin resistance.

Main Methods:

• Isolation and selection of Enterococcus faecium mutants resistant to mundticin KS.
• Determination of mutant sensitivity to nisin (class I bacteriocin) and kanamycin.
• Analysis of unsaturated fatty acid and phospholipid composition in wild-type and mutant strains.

Main Results:

• Two distinct types of mundticin KS-resistant mutants were identified with varying sensitivities to nisin and kanamycin.
• Resistant mutants maintained resistance to mundticin KS independently of Mg(2+) ions.
• Significant increases in unsaturated fatty acids and a specific zwitterionic phospholipid were observed in resistant mutants.
• Decreased levels of phosphatidylglycerol and cardiolipin were noted in the resistant mutants compared to the wild-type.

Conclusions:

• Physiological alterations, particularly in membrane lipid composition, are associated with resistance to class IIa bacteriocins like mundticin KS.
• These membrane changes may confer cross-resistance or altered sensitivity to other antimicrobial agents, including class I bacteriocins.
• Further research is needed to fully understand the implications of these findings for bacteriocin efficacy and food preservation.