Vancomycin resistance plasmids affect persistence of Enterococcus faecium in water

Area of Science:

• Environmental microbiology
• Antimicrobial resistance
• Bacterial genetics

Background:

• Vancomycin-resistant enterococci (VRE) cause significant nosocomial infections.
• VRE have been detected in sewage-contaminated surface waters, indicating potential environmental exposure and gene transfer.
• Antibiotic resistance genes may incur a fitness cost in non-optimal environments like surface waters.

Purpose of the Study:

• To investigate the impact of nutrients and vancomycin resistance plasmids on Enterococcus faecium survival in river water.
• To determine if plasmid size influences the fitness cost of antibiotic resistance in environmental settings.

Main Methods:

• Compared survival rates of VRE strains with and without vancomycin resistance plasmids in natural and nutrient-augmented river water.
• Measured strain decay rates using log10 reduction.
• Varied plasmid size in VRE strains to assess its effect on survival.

Main Results:

• In natural river water, larger plasmids correlated with faster VRE decay, indicating a fitness cost.
• Under nutrient-augmented conditions, plasmid presence and size did not significantly affect VRE decay rates.
• VRE with a 200 kb plasmid showed significantly higher decay in natural river water compared to susceptible strains.

Conclusions:

• Plasmids conferring antibiotic resistance can impact the fitness of Enterococcus species in environmental habitats like surface water.
• The fitness cost associated with antibiotic resistance plasmids is nutrient-dependent.
• Nutrient-rich sewage may prolong VRE survival in the environment, increasing risks of infection and gene transfer.