Detection of Porphyromonas gingivalis and Streptococcus intermedius in chronic periodontitis patients by multiplex PCR.

A Multiplex PCR assay for the detection of Porphyromonas gingivalis and Streptococcus intermedius in chronic periodontitis is presented. A total of 180 samples from 65 adults with untreated periodontitis and 17 healthy volunteers were taken and processed in a simple boiling step. Cell lysates were used as DNA source for multiplex PCR assays. Primers were designed from 16S rRNA gene sequences from the GenBank-EMBL database showing specificity for target pathogens. This multiplex PCR system could detect 8.2 P gingivalis and S. intermedius cells. In untreated periodontitis patients, only 78.5% were positive for one or both bacteria; 37% were positive for P gingivalis only, 17% for S. intermedius and 24.5% for both. P. gingivalis was detected in 23.5% of healthy volunteers, while S. intermedius was not detected in the same patients. The distribution of these bacteria was related to the periodontal probing depth, while 95.23% of patients with pockets wih 6 to 7 mm deep were positive for either or both, only 70.45% of of them with 4 to 5 mm pockets were positive.