In-vitro activity of erythromycin against anaerobic microorganisms

Minimum inhibitory concentrations of erythromycin were determined, in the absence of CO2, for 256 strains of anaerobic microorganisms recently isolated from clinical practice. Of 126 strains of Bacteroides fragilis, 93% were inhibited by 6 mg/L, or less, of erythromycin. Of the remaining 130 isolates, 92% were inhibited by 6 mg/L, or less, of erythromycin. These findings suggest that the majority of anaerobic microorganisms would be inhibited by the serum levels achieved by administering 1 g of erythromycin intravenously, every six hours.