Effects of metronidazole in patients with "refractory" periodontitis associated with Bacteroides forsythus

The aim of the present study was to monitor the microbiological and clinical effects of renewed supra- and subgingival debridement in conjunction with systemic metronidazole therapy (500 mg TID for 7 days) in 27 "refractory" periodontitis patients, culture positive for Bacteroides forsythus and negative for Actinobacillus actinomycetemcomitans. Clinical evaluation included assessment of plaque, bleeding upon probing, probing pocket depth and clinical attachment loss at the deepest, bleeding site in each quadrant. Microbiological evaluation was carried out by anaerobic cultivation of subgingival plaque samples from the same sites. 6 months after renewed debridement and systemic metronidazole (RD+M), a statistically significant improvement of all clinical parameters was observed, except for the plaque index. After RD+M, B. forsythus was suppressed below detection level in 17 of the 27 patients, P. gingivalis in 9 out of 15 patients and P. intermedia in 14 of the 21 patients. Before RD+M, 12 patients harboured simultaneously B. forsythus, P. gingivalis as well as P. intermedia. Out of these, 6 patients were culture negative for the 3 species after therapy and showed the greatest reduction in pocket depth (3.1 mm) and gain of clinical attachment level (2.5 mm). In the treatment of refractory periodontitis, associated with patients culture positive for B. forsythus and negative for A. actinomycetemcomitans, metronidazole can significantly improve the clinical and microbiological parameters.