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Bioactivity of flurithromycin and other macrolides against intracellular susceptible staphylococci
A Fietta1, P Boeri, M L Colombo
1Chair of Chemotherapy, University of Pavia, Italy.
Abstract:
The intracellular activity of flurithromycin, erythromycin, roxithromycin and miocamycin against susceptible clinical isolates of Staphylococcus aureus, phagocytosed by human monocytes, was investigated. Intracellular bioactivity was studied in a 24-hour assay, using experimental conditions which allowed the intracellular growth of bacteria. A colony counting method was used to differentiate between intracellular bacteriostatic and bactericidal activity of antibiotics. Moreover, the effect of macrolides against extracellular staphylococci was assessed. All agents showed higher intracellular than extracellular activity against staphylococci. At low concentration (0.1 mg/l) they had intracellular bacteriostatic activity. At concentrations higher than the minimal inhibitory ones (1 and 5 mg/l), miocamycin only still produced a bacteriostatic effect while flurithromycin, erythromycin and roxithromycin also showed intracellular bactericidal activity.
Insights
This study investigated macrolide antibiotics like flurithromycin and erythromycin against Staphylococcus aureus inside human monocytes. Flurithromycin, erythromycin, and roxithromycin demonstrated intracellular bactericidal activity at higher concentrations.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Staphylococcus aureus is a common pathogen.
- Intracellular activity of antibiotics is crucial for treating certain infections.
- Macrolides are a class of antibiotics with varying efficacy.
Purpose of the Study:
- To investigate the intracellular activity of flurithromycin, erythromycin, roxithromycin, and miocamycin against Staphylococcus aureus.
- To compare intracellular versus extracellular activity of these macrolides.
- To determine the bacteriostatic and bactericidal potential of macrolides within human monocytes.
Main Methods:
- Utilized a 24-hour assay with human monocytes phagocytosing Staphylococcus aureus.
- Employed a colony counting method to assess intracellular antibiotic effects.
- Evaluated both intracellular and extracellular activity of four macrolide antibiotics.
Main Results:
- All tested macrolides exhibited greater intracellular than extracellular activity against Staphylococcus aureus.
- At low concentrations (0.1 mg/l), all agents displayed intracellular bacteriostatic effects.
- At higher concentrations (1 and 5 mg/l), flurithromycin, erythromycin, and roxithromycin showed intracellular bactericidal activity, while miocamycin remained bacteriostatic.
Conclusions:
- Flurithromycin, erythromycin, and roxithromycin possess significant intracellular bactericidal activity against Staphylococcus aureus within monocytes.
- The intracellular efficacy of these macrolides is concentration-dependent.
- These findings highlight the potential of specific macrolides for treating intracellular Staphylococcus aureus infections.