THE TET(Q) GENE IN BACTERIA ISOLATED FROM PATIENTS WITH REFRACTORY PERIODONTAL-DISEASE

Twenty-two tetracycline-resistant (tet(r)) anaerobic and facultative a naerobic bacteria isolated from periodontal pockets of 12 patients wit h refractory periodontitis were examined for the presence of the Tet Q determinant by DNA-DNA hybridization. Dot blots of bacterial DNA were tested with an intragenic digoxigenin-labelled tet(Q) probe consistin g of a 1.45 kb EroRI/PvuII fragment from plasmid pNFD13-2. Southern bl ots of chromosomal DNA digested with the restriction enzyme EcoRI were also examined. The tet(Q) probe hybridized with DNA from 8 of the 22 tet(r) strains, including 2 Prevotella intermedia strains and one stra in each of Prevotella nigrescens, Prevotella loescheii, Prevotella ver oralis and Prevotella melaninogenica. The tet(r) strains of Mitsuokell a dentalis and Capnocytophaga ochracea also hybridized with the probe. The lack of discernible plasmid DNA in all the probe-positive isolate s suggests that these tetracycline-resistance genes were chromosomally encoded. The probe hybridized with a different size fragment in all t he isolates. This study extends the number of species that carry the t et(Q) gene to include several outside the genera Prevotella and Bacter oides.