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Comparison of clindamycin, erythromycin, and methicillin in streptococcal infections in monkeys
Abstract:
Intravenous inoculation of a group A hemolytic streptococcus caused lethal infections in all of eight untreated monkeys. Intramuscular injections of clindamycin-2-phosphate in a daily dose of 25 mg/kg given in equal morning and afternoon doses for 10 days resulted in survival of all of eight monkeys. Similar results were observed with the same dose schedule of clindamycin hydrochloride given intragastrically; no fatalities occurred among eight monkeys. In monkeys receiving erythromycin stearate intragastrically or methicillin intramuscularly, three of eight and four of eight monkeys, respectively, died. Duration of both illness and positive blood cultures was greater in the erythromycin- and methicillin-treated survivors than in the clindamycin-treated monkeys. The differences in results between clindamycin and erythromycin could not be correlated with serum antibacterial activity levels, which were similar, or with minimal inhibitory concentrations, which were 0.02 mug/ml with both antibiotics. With methicillin, however, the minimal inhibitory concentration was 0.16 mug/ml and serum antibacterial activity varied from titers of less than 1:2 to 1:8. As in previous studies of staphylococcal infections in monkeys with the same antibiotics, in vitro susceptibility data and serum antibacterial activity did not completely correlate with in vivo results.
Insights
Clindamycin effectively treated group A hemolytic streptococcus infections in monkeys, preventing fatalities. Other antibiotics like erythromycin and methicillin showed lower efficacy, with higher mortality rates and prolonged illness in survivors.
Area of Science:
- Infectious Diseases
- Pharmacology
- Microbiology
Background:
- Group A hemolytic streptococcus infections can be severe and life-threatening.
- Antibiotic efficacy in treating streptococcal infections requires thorough investigation.
Purpose of the Study:
- To evaluate the efficacy of clindamycin, erythromycin, and methicillin against group A hemolytic streptococcus in a primate model.
- To compare treatment outcomes and correlate them with in vitro susceptibility and serum antibacterial activity.
Main Methods:
- Monkeys were inoculated with group A hemolytic streptococcus.
- Treatment groups received clindamycin (intramuscular or intragastric), erythromycin (intragastric), or methicillin (intramuscular).
- Survival rates, duration of illness, and positive blood cultures were monitored. In vitro minimum inhibitory concentrations (MICs) and serum antibacterial activity were assessed.
Main Results:
- Clindamycin administration resulted in 100% survival, while erythromycin and methicillin showed lower survival rates (62.5% and 50%, respectively).
- Untreated monkeys experienced 100% mortality.
- Clindamycin-treated survivors had shorter durations of illness and positive blood cultures compared to survivors treated with erythromycin or methicillin.
Conclusions:
- Clindamycin demonstrated superior efficacy in treating experimental group A hemolytic streptococcus infections in monkeys compared to erythromycin and methicillin.
- In vitro susceptibility and serum activity did not fully predict in vivo treatment outcomes, highlighting the complexity of antibiotic effectiveness.
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