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In vitro antimicrobial effects of various combinations of penicillin and clindamycin against four strains of
D L Stevens1, K J Madaras-Kelly, D M Richards
1Infectious Diseases Section, VA Medical Center, Boise, Idaho 83702, USA. dlsteven@primenet.com
Abstract:
Previous studies using mouse models of Streptococcus pyogenes necrotizing fasciitis demonstrated that clindamycin had greater efficacy than penicillin. Frequently both agents are used concurrently in the treatment of severe S. pyogenes infections. This study investigated interactions between penicillin and clindamycin. E-test and broth microdilution assays suggested additivity or indifference, while timed-killing assays demonstrated concentration-dependent variable effects. Timed-kill studies utilizing clinical concentrations suggest that there is no antagonism with the combination of drugs but that the combination does not have a bactericidal advantage over either penicillin or clindamycin alone.
Insights
This study found that combining penicillin and clindamycin for Streptococcus pyogenes infections showed no antagonism but no added bactericidal benefit over single-drug use.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Severe Streptococcus pyogenes infections, like necrotizing fasciitis, are often treated with penicillin and clindamycin concurrently.
- Previous research indicated clindamycin monotherapy may be more effective than penicillin in mouse models.
Purpose of the Study:
- To investigate the in vitro interaction between penicillin and clindamycin against Streptococcus pyogenes.
- To determine if the combination therapy offers synergistic or additive bactericidal effects compared to monotherapy.
Main Methods:
- Utilized E-test and broth microdilution assays to assess drug interactions.
- Performed time-kill assays at clinically relevant concentrations to evaluate bactericidal activity.
Main Results:
- E-test and microdilution assays suggested additive or indifferent interactions between penicillin and clindamycin.
- Time-kill assays revealed concentration-dependent effects, with no observed antagonism.
- The combination did not demonstrate a significant bactericidal advantage over either penicillin or clindamycin alone.
Conclusions:
- Concurrent use of penicillin and clindamycin for severe S. pyogenes infections is not antagonistic.
- The combination therapy does not provide enhanced bactericidal activity compared to monotherapy with either agent.