The Effect of Clindamycin on the Microbiota Associated With Refractory Periodontitis

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Abstract
The purpose of this investigation was to determine the effect of clindamycin hydrochloride, as an adjunct to scaling, on the microbiota associated with refractory periodontitis and to elucidate the probable causative bacteria associated with the disease. Microbial samples were collected from a subset of 9 patients with severe adult periodontitis who had not responded to conventional treatment modalities including the use of tetracycline and other antibiotics. Microbial samples were collected from a relatively deep site determined to be actively losing attachment and a comparably deep, but quiescent, control site in each patient prior to clindamycin therapy. Samples continued to be collected from the same sites for up to 1 year post‐therapy. The microbial flora of each sample were enumerated by darkfield microscopy and predominant cultivable methods. Prior to clindamycin therapy, both active and control sites consisted on average of approximately 50% spirochetes and motile rods and 40% Gram‐negative anaerobic rods. Bacteroides intermedius and Porphyromonas gingivalis (formerly B. gingivalis) were elevated in the active, as compared to control, sites and accounted for approximately 20% of the cultured microbiota in the former. Following treatment with clindamycin, the Gram‐negative components of the microbiota were either eliminated or severely suppressed. At 1 year post‐therapy, spirochetes and motile rods together accounted for about 15% of the microscopic flora. Total Gram‐negative anaerobic rods accounted for approximately 20%, and B. intermedius and P. gingivalis combined accounted for less than 2% of the cultured microbiota from historical active sites. Antibiotic susceptibilities were determined using strains isolated prior to and at 1 year after therapy. No significant increases in 6 bacteria resistant to clindamycin were noted in the post‐therapy microbiota. The suppression of the Gram‐negative portion of the microbiota coincided with previously reported clinical improvements obtained following the adjunctive use of clindamycin. J Periodontol 1990; 61:692–698.