Susceptibility of human oral anaerobic bacteria to antibiotics suitable for topical use

17 antibiotics, with potential for topical use, were tested for their activity against the human oral flora. Concentrations (mumol/l) required to inhibit 90% of test strains are presented and drug activities are compared. The total cultivable oral flora was susceptible to the tetracyclines including tetracycline itself, minocycline, doxycycline, and oxytetracycline and to erythromycin. On the other hand, actinobolin, kanamycin, neomycin, streptomycin, spiramycin, tyrothricin, vancomycin, clindamycin, and chloramphenicol were ineffective against many of the human oral anaerobic bacteria even at high concentration. Penicillin was effective at high concentrations but could not be recommended because organisms which are not inhibited by low concentrations are penicillinase producers. Carbenicillin was effective against all organisms except Actinobacillus actinomycetemcomitans. The gram-negative organisms involved in adult periodontitis were most susceptible to the tetracyclines, tyrothricin, carbenicillin and clindamycin, while those associated with localized juvenile periodontitis were susceptible to the tetracyclines or erythromycin. These data, combined with the previous findings that some tetracyclines exhibit marked substantivity and collagenase inhibition activity, indicate that tetracycline or minocycline are likely to be good choices in the treatment or prevention of oral diseases.