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Comparative bactericidal activity of penicillin-netilmicin and penicillin-gentamicin against enterococci
Abstract:
The synergistic bactericidal activity of netilmicin in combination with penicillins was compared with that of gentamicin and streptomycin against 16 clinical isolates of enterococci. In a macrodilution chessboard assay against multiple combinations of penicillin, gentamicin and netilmicin, bactericidal activity uniformly occurred at two- to four-fold lower concentrations of penicillin + netilmicin than with penicillin + gentamicin. With four strains, penicillin + netilmicin produced up to ten-fold greater killing than penicillin + gentamicin after 6 h of incubation. With one strain, 3 X log10 greater killing occurred with netilmicin after 24 h. Netilmicin was two- to four-fold more active than gentamicin when combined with penicillinase-resistant penicillins. The bactericidal activity of netilmicin against enterococci is equal to or greater than that of gentamicin, either alone or when combined with penicillins.
Insights
Netilmicin combined with penicillins shows superior bactericidal activity against enterococci compared to gentamicin. This combination offers enhanced killing power, suggesting improved therapeutic potential for enterococcal infections.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Enterococci are significant causes of nosocomial infections.
- Antibiotic resistance in enterococci necessitates the evaluation of alternative therapeutic strategies.
- Aminoglycosides, such as gentamicin and netilmicin, are often used in combination with cell-wall active agents like penicillins for treating enterococcal infections.
Purpose of the Study:
- To compare the synergistic bactericidal activity of netilmicin plus penicillins with that of gentamicin plus penicillins against clinical isolates of enterococci.
- To evaluate the comparative efficacy of netilmicin and gentamicin when combined with various penicillins.
Main Methods:
- A macrodilution chessboard assay was employed to assess the synergistic bactericidal activity.
- The study included 16 clinical isolates of enterococci.
- Combinations tested included netilmicin/penicillin, gentamicin/penicillin, and streptomycin/penicillin.
Main Results:
- Penicillin plus netilmicin demonstrated synergistic bactericidal activity at two- to four-fold lower concentrations compared to penicillin plus gentamicin.
- Penicillin plus netilmicin achieved up to ten-fold greater killing than penicillin plus gentamicin after 6 hours of incubation for four strains.
- Netilmicin exhibited two- to four-fold greater activity than gentamicin when combined with penicillinase-resistant penicillins.
Conclusions:
- Netilmicin demonstrates equal or greater bactericidal activity against enterococci than gentamicin, both alone and in combination with penicillins.
- The combination of netilmicin and penicillins offers a potentially more effective therapeutic option for enterococcal infections compared to gentamicin-based regimens.