Nutrient-induced antibiotic resistance in Enterococcus faecalis in the eutrophic environment

Area of Science:

• Environmental Microbiology
• Ecotoxicology
• Antimicrobial Resistance

Background:

• Rising global nutrient deposition and antibiotic use impact freshwater ecosystems.
• Bacteria, including Enterococcus faecalis, can develop and maintain antibiotic resistance in eutrophic environments.

Purpose of the Study:

• To investigate the influence of nitrogen (N) and phosphorus (P) on antibiotic resistance phenotypes and resistance genes in Enterococcus faecalis.
• To assess the ecological effects of nutrient influx on bacterial antibiotic resistance in model freshwater ecosystems.

Main Methods:

• Established replicated mesocosms with four N and P regimens.
• Isolated Enterococcus faecalis strains over 95 days to test sensitivity to ampicillin, oxytetracycline, ciprofloxacin, chloramphenicol, vancomycin, and erythromycin.
• Utilized PCR to detect specific antibiotic resistance genes (ermB, msrC, mefA, tet(M), tet(L), tet(S), cat, esp) and monitored water quality parameters.

Main Results:

• N and P addition significantly altered E. faecalis resistance to oxytetracycline, chloramphenicol, and erythromycin.
• High N and P dosages induced ciprofloxacin resistance.
• Elevated total nitrogen concentrations correlated with increased resistance to oxytetracycline and ciprofloxacin.
• Specific resistance genes, including tet(L), tet(S), msrC, and cat, were associated with observed resistance phenotypes.

Conclusions:

• Nutrient enrichment in freshwater ecosystems significantly impacts the antibiotic resistance profiles of Enterococcus faecalis.
• The study highlights the link between nutrient pollution, antibiotic resistance development, and the prevalence of specific resistance genes in aquatic bacteria.