title: Resistance of Actinobacillus actinomycetemcomitans and differential susceptibility of oral Haemophilus species to the bactericidal effects of hydrogen peroxide.
abstract: We compared the sensitivities of oral and nonoral isolates of Actinobacillus actinomycetemcomitans, Haemophilus segnis, H. aphrophilus, and H. paraphrophilus to the bactericidal action of reagent hydrogen peroxide (H2O2). Susceptibility to a range of H2O2 concentrations (10(-6) to 10(-3) M) was assessed by incubating bacterial suspensions for 1 h at 37 degrees C in the presence of H2O2 and plating on chocolate agar to determine the concentration of H2O2 that would produce a 50% reduction in CFU (50% lethal dose). As a group, A. actinomycetemcomitans was more resistant to H2O2 than the oral haemophili, and H. aphrophilus was much more sensitive than all other organisms tested. The range of 50% lethal dose values for A. actinomycetemcomitans was between 8.5 X 10(-5) and 10(-3) M H2O2 or above. In contrast, H. aphrophilus exhibited 50% lethal dose values from below 1 X 10(-6) to 3.4 X 10(-4) M H2O2. The resistance of A. actinomycetemcomitans to H2O2 may be sufficient to protect these organisms from direct H2O2-mediated killing by host phagocytes.
mesh_terms: D000188:Actinobacillus / Q000187:drug effects*; D003773:Dental Plaque / Q000382:microbiology; D004352:Drug Resistance, Microbial; D006190:Haemophilus / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007700:Kinetics
chemical_list: D006861:Hydrogen Peroxide