Synergy between penicillin and gentamicin against enterococci

Area of Science:

• Microbiology
• Pharmacology
• Biochemistry

Background:

• Enterococci are opportunistic pathogens.
• Aminoglycosides like gentamicin are crucial antibiotics.
• Penicillin can enhance aminoglycoside efficacy but requires understanding of mechanisms.

Purpose of the Study:

• To investigate the role of active uptake in gentamicin's enhanced activity against penicillin-treated enterococci.
• To elucidate the energy dependence of this synergistic effect.

Main Methods:

• Viable counts and ATP determinations were used.
• Experiments involved synergistic treatments with penicillin and gentamicin.
• Electron transport inhibition (sodium azide) and divalent cation chelation (EDTA) were employed.

Main Results:

• Penicillin and gentamicin exhibited synergistic bactericidal and post-antibiotic effects (PAEs).
• Sodium azide partially reduced these effects, while sodium azide plus EDTA completely blocked them.
• EDTA and gentamicin also showed marked synergy, inhibited by sodium azide.

Conclusions:

• Gentamicin's activity against penicillin- or EDTA-damaged enterococci is energy-dependent.
• This supports the theory of gentamicin uptake driven by protonmotive force.