METRONIDAZOLE SUSCEPTIBILITY FACTORS IN ACTINOBACILLUS-ACTINOMYCETEMCOMITANS

Actinobacillus actinomycetemcomitans is a facultative anaerobic bacter ium that displays moderate susceptibility to metronidazole and this st udy was undertaken to identify the factors involved. A. actinomycetemc omitans appeared two to four times less susceptible to metronidazole w hen grown in air supplemented with 5% CO2 than under anaerobic conditi ons. Ferredoxin-linked pyruvate: oxidoreductase activity was absent bu t each strain exhibited nitroreductase activity which corresponded dir ectly with uptake of metronidazole and susceptibility to the drug unde r anaerobic conditions but not in air supplemented with 5% CO2. Nitror eductase activity therefore appears responsible for the susceptibility of A. actinomycetemcomitans to metronidazole.