SUBGINGIVAL DISTRIBUTION OF PERIODONTOPATHIC BACTERIA IN ADULT PERIODONTITIS AND THEIR SUSCEPTIBILITY TO MINOCYCLINE-HCL

THE PURPOSE OF THIS STUDY was to investigate the distribution of sever al periodontopathic bacteria in adult periodontitis, their in vitro su sceptibility to minocycline-HCl, and whether the efficacy of the drug changes with a decrease in bacterial susceptibility. Twenty-one patien ts (43 to 75 years old) with 62 periodontal lesions from pockets great er than or equal to 4 mm participated in the study. After subgingival sampling, an ointment containing 2% minocycline-HCl was applied locall y to the selected pockets once a week for 4 weeks. The lesions were cl inically examined after 1 and 4 weeks of administration. The distribut ion of the subgingival microorganisms included Capnocytophaga sputigen a (37.1%), Prevorella intermedia (22.6%), Porphyromonas gingivalis (22 .6%), Fusobacterium nucleatum (20.1%), Actinobacillus actinomycetemcom itans (9.7%), and Eikenella corrodens (4.8%). The distribution was com plex, with 76.8% of the sites containing 1 to 3 bacterial spieces. The minimum inhibitory concentration (MIG) of minocycline-HCl for each or ganism showed that most were inhibited by a minocycline-HCl concentrat ion equal to or less than the MIC for reference strains. However, some clinical strains of Prevotella intermedia seemed to exihibit low susc eptibility to minocycline-HCl. There were no significant differences a mong sites with strains exhibiting low or normal susceptibility to min ocycline-HCl. The concentration of the drug applied to deep periodonta l pockets inhibited the growth of most of the microorganisms investiga ted in this study.