Detection and incidence of the tetracycline resistance determinant in the microflora associated with adult periodontitis
The purpose of this paper is to determine the incidence of the set(M) gene in this bacterial population as a first step to account for the molecular basis of tetracycline resistance in the subgingival flora and to develop a polymerase chain reaction assay of the set(M) determinant. Subgingival plaque samples were collected from six different sites, 5 mm or deeper, with sterile paper points in 68 patients. Samples were plated onto duplicate Trypticase soy blood agar, one set with tetracycline HCl and the other set without any antibiotic. Polymerase chain reaction was used to detect tet (M) in the samples and in the subcultured isolates. Results indicate that tetracycline-resistant bacteria represented approximately 12% of the total viable count. The percentage of set(M) positive bacteria in the tetracycline-resistant microflora varied from 0.05 to 83%. Tet(M) was detected in 60% of 204 tetracycline-resistant strains subcultured and identified. The tet (M)-containing strains consisted of streptococci, actinomyces, bifidobacterium, and Veillonella spp. Tetracycline-resistant strains in which set(M) was not detected included the Prevotella and Bacteroides species. These results suggests that set(M) is widely spread in the adult periodontal microflora, but it appears, with the exception of S intermedius, to be mainly associated with microorganisms not considered to be periodontopathogens. [P.W.]
Lacroix, J.-M., and C.B.Walker, J Periodont, 66:102, 1995