Local antibiotic therapy guided by microbiological diagnosis.

Abstract

The aim of this study was to determine the distribution patterns of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans in periodontitis patients after standard mechanical periodontal therapy, and to evaluate the effect of additional local antibiotic therapy, given to all teeth with cultural evidence of these bacteria. 17 patients were included. 852 separate subgingival microbial samples were taken from the mesial and distal aspect of every tooth in 17 subjects at baseline. 46 of these samples, from 10 positive subjects, showed cultural evidence for P. gingivalis. 82 samples, from 5 subjects, were A. actinomycetemcomitans-positive. Three subjects showed no evidence for persistence of A. actinomycetemcomitans or P. gingivalis. In the other 14 subjects, all A. actinomycetemcomitans- or P. gingivalis-positive teeth were treated with tetracycline fibers (ACTISITE(R)). Sub-gingival microbial samples were again taken from two sites of every tooth, 1 month after fiber removal. 89% of the initially P. gingivalis-positive sites were now negative, but 16 previously negative sites now tested positive. 77% of the initially A. actinomycetemcomitans-positive sites were now negative, but 5 previously negative sites now tested positive. The teeth with persisting P. gingivalis or A. actinomycetemcomitans were again treated with fibers. Two sites of every tooth were once more sampled after 1 month. At this time, 5 subjects still showed cultural evidence of P. gingivalis at a total of 19 sites, and 4 subjects were positive for A. actinomycetemcomitans in a total of 27 sites. These 9 patients were finally submitted to systemic antibiotic therapy (3 x 250 mg metronidazole plus 3 x 375 mg amoxicillin/d for 7 days). Despite of all efforts, P. gingivalis was again detected 3 months later in isolated sites in 3 subjects, and A. actinomycetemcomitans could be cultivated from one single site. Therapy with tetracycline fibers guided by microbiological diagnosis effectively reduced P. gingivalis and A. actinomycetemcomitans locally, but was unable to completely eradicate the target organisms. Additional systemic antibiotic therapy further reduced P. gingivalis and A. actinomycetemcomitans. The observed persistence patterns suggest that reemergence of A. actinomycetemcomitans was due to recolonization, whereas the strikingly reproducible local reemergence of P. gingivalis in some sites indicated failed eradication.