Subgingival microflora of periodontal patients on tetracycline therapy

Abstract

Samples of subgingival plaque were collected from periodontal patients receiving two different tetracycline treatment regimens following conventional periodontal therapy. Four patients had received an oral dose of 1000 mg/day for 2 weeks and nine had received 1000 mg/day for 1 week followed by 250 mg/day for extended time periods. The latter regimen is similar so that commonly prescribed for the chronic skin disease, acne vulgaris. Taxonomic characterization of plaque isolates indicated that the predominant organisms cultured from both treatment groups were species of Streptococcus and the branching, filamentous Gram-positive rods, Actinomyces and Rothia. A much greater microbial complexity was observed among the flora isolated from patients taking 250 mg/day. The latter group harbored many of the fastidious Gram-negative organisms presently implicated in the etiology of periodontal disease. All bacterial strains isolated were tested for resistance to tetracycline by replica-plating cultures on an agar medium containing two-fold dilutions of the antibiotic. Streptococcus, Veillonella and Neisseria were the bacterial genera found to be consistently resistant to tetracycline, with minimum inhibitory concentrations as high as 128 micrograms/ml. Among the Actinomyces, selection for antibiotic resistance was common only within a single species, A. odontolyticus. However, A viscosus strains isolated at 54% of the subgingival flora from one patient did demonstrate an intermediate resistance level, growing on concentrations up to 8 micrograms/ml. Tetracycline resistance was shown by a variety of Gram-negative rods isolated from the low dosage group. Although a minimum number of patients were studied, extensive microbial analyses of the predominating subgingival bacteria indicated that the goal of tetracycline therapy was achieved during the 2-week therapy period at 1000 mg/day.

Effects of tetracycline on the streptococcal flora of periodontal pockets

“…In these latter investigations, the patients were treated by conventional means before antibiotic therapy, and attempts were made to isolate anaerobes, as well as the total facultative population, from periodontal pockets. The results suggested that after a 2-week tetracycline regimen, streptococci predominated (39). However, a much greater microbial complexity was observed, including resistant gramnegative subgingival organisms, when the antibiotic was administered for extended periods of time (34,39).…”

“…The results suggested that after a 2-week tetracycline regimen, streptococci predominated (39). However, a much greater microbial complexity was observed, including resistant gramnegative subgingival organisms, when the antibiotic was administered for extended periods of time (34,39). A primary objective of this study was to determine the extent of plasmid-associated tetracycline resistance within the oral streptococcal flora.…”

“…Unlike many of the results previously obtained with the Enterobacteriaceae (11), selection with a single antibiotic did not lead to the isolation of multiply resistant oral streptococci. (34,39). In these latter investigations, the patients were treated by conventional means before antibiotic therapy, and attempts were made to isolate anaerobes, as well as the total facultative population, from periodontal pockets.…”

Interaction between Streptococcus spp. and Veillonella tobetsuensis in the Early Stages of Oral Biofilm Formation

“…Additionally, these bacteria, like other anaerobes, are susceptible to various antimicrobials; however, several of these species are resistant to tetracycline. In periodontal patients undergoing therapy, Veillonella species, along with Streptococcus and Neisseria species, were found to be consistently resistant to tetracycline (30). Moreover, tetracycline-resistant Veillonella species have the opportunity to come in close contact with and, consequently, transfer resistance elements to other oral bacteria and the bacteria that pass through the oral cavity (31).…”

Gingival crevicular fluid levels of clindamycin compared with its minimal inhibitory concentrations for periodontal bacteria

“…Periodontol., in press) have shown that tetracycline is delivered in sufficient quantities to inhibit most organisms at the site of infection, which in periodontal diseases is the pocket or space between the teeth and the gingiva. However, resistance to this drug is not uncommon (15,18) and may account for patients who continue to lose alveolar bone despite conventional therapy and the adjunctive use of tetracycline. In some patients, susceptibility data have indicated that penicillin may be as effective as tetracycline (7,15).…”