Antibiotic susceptibility testing of anaerobic bacteria by the standardized disc diffusion method with special reference to bacteroides fragilis.

The susceptibility of 90 strains of Bacteroides fragilis to 16 antibacterial drugs was determined by the agar plate dilution test and the disc diffusion test. Good correlation of results was obtained with the two methods, and regression line analysis could be performed for beta-lactam antibiotics, erythromycin, tetracyclines, lincomycin and clindamycin. Thus the standardized disc diffusion method can be used for susceptibility testing, but only a clear distinction between sensitive and resistant strains can be seen.