DETECTION OF IDENTICAL RIBOTYPES OF PORPHYROMONAS-GINGIVALIS IN PATIENTS RESIDING IN THE UNITED-STATES, SUDAN, ROMANIA AND NORWAY

Porphyromonas gingivalis has been isolated from periodontitis lesions in subjects from many geographical locations. The purpose of this inve stigation was to determine whether similar ribotypes of P. gingivalis could be detected among strains isolated in different countries. A tot al of 198 isolates of P. gingivalis were obtained from 52 periodontiti s patients in Boston (130 isolates), Bergen, Norway (17 isolates), Kha rtoum, Sudan (26 isolates), and Bucharest, Romania (25 isolates). DNA was isolated from each strain, cut separately by the restriction endon ucleases KpnI and PstI. The resulting preparations were subjected to e lectrophoresis in a 0.8% agarose gel using a Tris-acetate EDTA buffer. Uncut lambda and a 1000-bp fragment of 16S rRNA were included as inte rnal standards in each lane. In addition, a HindIII digest of lambda w as present in a separate lane in each run. The DNA fragments were tran sferred to a nylon membrane by downward capillary transfer. 16S rRNA b ands were detected using a 1000-kb digoxigenin-labelled probe generate d by a polymerase chain reaction. At the same time, a digoxigenin-labe lled probe to lambda was employed to detect the internal and molecular weight standards. The bands were detected using antibody to digoxigen in conjugated to alkaline phosphatase and chemiluminescence. The posit ions of the bands relative to the internal standards were determined a nd normalized to correct for run-to-run variations, and the molecular weight of each band was determined by comparison with standards within each gel. The resulting data for the 2 enzymes were combined and subj ected to cluster analysis using an average unweighted linkage sort. In some instances, isolates that appeared to be of identical ribotype us ing one endonuclease gave different ribotypes using the other. Strains of P. gingivalis within a subject were usually identical, except for 3 patients who harbored 2 different ribotypes/individual. All subseque nt analyses employed a single ribotype strain for each subject. A tota l of 32 ribotypes were observed for isolates from distant countries. A total of 11.5% of the patients had isolates exhibiting the same ribot ype: ribotype 7a. Identical ribotypes of P. gingivalis can be recovere d from subgingival plaque samples of periodontitis patients in differe nt countries.