Invasion of endothelial and epithelial cells by strains of Porphyromonas gingivalis

Porphyromonas gingivalis is a periodontal pathogen that may also be involve d in the pathogenesis of coronary heart disease. This microorganism has the ability to invade several cell lines. In this study, 25 different strains of P, gingivalis were tested for invasion of human umbilical vein endotheli al cells and KB cells, a human oral epidermoid cell line. Abilities to inva de both cell lines by an individual strain were similar, and their invasion efficiencies could be assembled into four groups: high, moderate, low and non-invasive. Of the 36 strains, only P, gingivalis AJW4 was non-invasive. Since the fimbriae are implicated as having a key role in invasion by this species, the presence of fimbriae on strain AJW4 was investigated. Using po lymerase chain reaction (PCR), strain AJW4 was found to contain the fimA ge ne. Sequence analysis revealed it to be type IV according to the typing sch eme developed by Amano et al. Further fimA is transcribed in this strain as demonstrated by reverse transcription PCR and is expressed on the cell sur face as visualized by negative staining and electron microscopy. The adhere nce + invasion of strain AJW4 was 38.7% of the most invasive strain (strain 381). However, the CFU ml(-1) of strain AJW4 recovered from within cells w as 2.9% of strain 381. Even though strains AJW4 and W50 have the same type IV fimbriae, strain AJW4 is 8.9-fold more adhesive yet is internalized 170- fold less. These data indicate that the invasion efficiency of P. gingivali s is variable among the different strains, and that the expression of FimA is not sufficient for invasion. (C) 2000 Federation of European Microbiolog ical Societies. Published by Elsevier Science B.V. All rights reserved.