Agar medium for use in susceptibility testing of bacteria from human periodontal pockets.

An agar medium (medium V) was formulated to determine the minimal inhibitory concentrations (MICs) of antimicrobial agents for bacteria encountered in human periodontal pockets. The medium contained (per liter) Trypticase, 15 g; yeast extract, 5 g; sodium chloride, 5 g; glucose, 2 g; sodium pyruvate, 2 g; sodium formate, 1 g; sodium fumarate, 1.5 g; sodium succinate, 0.1 g; Tween 80, 0.25 ml; agar, 15 g; hemin, 5 mg; and menadione, 0.5 mg. The growth of 50 oral strains was compared on this and six other media which included: Wilkins-Chalgren agar, Schaedler agar, Brucella agar, Trypticase-soy blood agar, and Schaedler and Brucella agars supplemented with whole blood. Growth, for most strains, was greatest on medium V. Medium V was also compared with Wilkins-Chalgren agar, using the same oral strains, to determine the MICs of the following antibiotics: penicillin, tetracycline, chloramphenicol, clindamycin, and erythromycin. The MICs of these antibiotics were essentially the same on both media when growth was quantitatively similar.