Antibiotic disc susceptibility tests for rapid presumptive identification of Gram-negative anaerobic bacilli

A method for identification of gram-negative anaerobic bacilli is described. Based on differences in susceptibility to paper discs containing 10 mug of colistin, 60 mug of erythromycin, 1,000 mug of kanamycin, 1,000 mug of neomycin, 2 units of penicillin, and 15 mug of rifampin, these bacteria may be placed into five groups. Other tests such as colony morphology, production of pigment, growth in bile, esculin hydrolysis, and reaction on egg yolk-agar may be used for further identification. The susceptibility tests are rapid and simple to perform and are helpful in characterizing gram-negative anaerobic bacilli. They are not intended for use in predicting clinical effectiveness of the drugs utilized.