New rapid polymerase chain reaction-immunochromatographic assay for Porphyromonas gingivalis

Background: A simple and rapid method for Porphyromonas gingivalis detection in clinical samples has been developed using polymerase chain reaction (PCR) and an immunochromatographic assay (ICA) with a lateral-flow device (strip) to detect species-specific 16S rRNA genes. Methods: The PCR used a pair of primer sets labeled with fluorescein isothiocyanate (FITC) or biotin at each 5' terminus. The strip used a nitrocellulose membrane containing streptavidin conjugated to gold particles and anti-FITC line. Results: PCR and ICA detected as few as 1 and 10 cells of P gingivalis, respectively. ICA required 5 to 10 minutes more than the initial PCR. The amplifications were not observed in other oral black-pigmented bacteria at concentrations of 10(6) colony forming unit (CFU). The ICA strips showed bands at more than 10(4) CFU/ml equivalents in clinical samples from periodontitis. Conclusions: A diagnostic assay based on PCR-ICA was developed for the detection of P gingivalis, and results were obtained visually in 3 hours. PCR-ICA will be a valuable tool for the rapid detection of target bacteria by chair side.