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Synergy characterization for Enterococcus faecalis strains displaying moderately high-level gentamicin and
C E Bantar1, M Micucci, L Fernandez Canigia
1Laboratorio de Bacteriología Clínica, Centro de Educación Médica e Investigaciones Clínicas, Buenos Aires, Argentina.
Abstract:
Synergy of 14 Enterococcus faecalis strains displaying moderately high-level aminoglycoside resistance (MICs, 500 and 256 to 1,000 micrograms/ml for gentamicin and streptomycin, respectively) was characterized by time-kill studies. All strains proved resistant to penicillin plus the respective aminoglycoside. Strains with moderately high-level aminoglycoside resistance should be considered to exhibit high-level resistance in severe infections.
Insights
Fourteen Enterococcus faecalis strains showed synergy when treated with aminoglycoside antibiotics, despite initial resistance. These findings suggest that even moderately resistant strains should be treated as highly resistant in severe infections.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Enterococcus faecalis is an opportunistic pathogen.
- Aminoglycoside resistance in E. faecalis can complicate treatment.
- Understanding resistance synergy is crucial for effective antimicrobial therapy.
Purpose of the Study:
- To investigate the synergistic effects of aminoglycoside antibiotics in Enterococcus faecalis strains with moderate-to-high level resistance.
- To evaluate the efficacy of combined penicillin and aminoglycoside therapy against these resistant strains.
Main Methods:
- Time-kill studies were employed to assess bacterial killing kinetics.
- Minimum Inhibitory Concentrations (MICs) were determined for gentamicin and streptomycin.
- Synergy was evaluated for combinations of penicillin with aminoglycosides.
Main Results:
- Fourteen Enterococcus faecalis strains exhibited moderately high-level aminoglycoside resistance (MICs: gentamicin 500 µg/ml, streptomycin 256-1000 µg/ml).
- All tested strains were resistant to penicillin in combination with the respective aminoglycoside.
- Synergistic effects were observed, but clinical resistance persisted.
Conclusions:
- Enterococcus faecalis strains with moderately high-level aminoglycoside resistance demonstrate resistance to penicillin-aminoglycoside combinations.
- In severe infections, strains with moderately high-level aminoglycoside resistance should be clinically considered as high-level resistant.
- Further research into novel therapeutic strategies is warranted.