Microbiological and clinical results of metronidazole plus amoxicillin therapy in Actinobacillus actinomycetemcomitans-associated periodontitis.

We report on the microbiological and clinical effects of mechanical debridement in combination with metronidazole plus amoxicillin therapy in 118 patients with Actinobacillus actinomycetemcomitans-associated periodontitis. Patients were categorized into 3 groups: 28 had localized periodontitis; 50 had generalized periodontitis, and 40 had refractory periodontitis. After initial treatment and metronidazole plus amoxicillin therapy 114 of 118 (96.6%) patients had no detectable A. actinomycetemcomitans. Significant reduction in pocket probing depth and gain of clinical attachment were achieved in almost all patients. Four patients were still positive for A. actinomycetemcomitans after therapy. Metronidazole resistance (MIC greater than 25 micrograms/ml) was observed in 2 of 4 strains from these patients. Patients still positive for A. actinomycetemcomitans or Porphyromonas gingivalis showed a significant higher bleeding tendency after therapy. It was concluded that mechanical periodontal treatment in combination with the metronidazole plus amoxicillin therapy is effective for subgingival suppression of A. actinomycetemcomitans in patients with severe periodontitis.