Comparison of fluorescence microscopy and culture assays to quantitate adhesion of Porphyromonas gingivalis to mono- and multi-layered pocket epithelium cultures
W. Papaioannou et al., Comparison of fluorescence microscopy and culture assays to quantitate adhesion of Porphyromonas gingivalis to mono- and multi-layered pocket epithelium cultures, J PERIODONT, 70(6), 1999, pp. 618-625
Background: The present study compared 2 different methods (direct versus i
ndirect evaluation) for the quantification of the adhesion of Porphyromonas
gingivalis strains to in vitro cultured monolayers of pocket epithelium.
Methods: The indirect culture viability assay (calculation of colony formin
g units) was compared to a direct microscopic evaluation using a novel fluo
rescent stain. The fluorescent kit was found to stain both bacteria and epi
thelial cells and enabled a differentiation between dead and living cells.
Results: Comparing the visual to the culture data, a high and significant c
orrelation was found (Pearson's correlation = 0.75; P < 0.001). The adhesio
n capacity was in general higher for dead epithelial cells than for living
cells (P < 0.01). Although comparable numbers of bacteria of 2 P. gingivali
s strains (Pg 4 and Pg 5) were applied, Pg 4 showed a significantly lower a
dhesion capacity. This intra-strain variability was observed by the culture
assay (2.3 x 10(6) versus 7.8 x 10(6) +/- 2.7 x 10(6); P < 0.01) and by th
e direct microscopy (P < 0.01) for both live and dead epithelial cells. A s
econd goal was to see whether there was a difference in the amount of bacte
rial adherence to mono- and multi-layers of in vitro cultured epithelium. N
o significant differences were found for the 5 examined P. gingivalis strai
ns. However, interstrain differences in adhesion capacity were evident for
both tissues.
Conclusions: This study highlights the reproducibility of a direct microsco
pic evaluation of bacterial adhesion to in vitro cultured epithelial cells,
and suggests both intrastrain (P. gingivalis) and inter-cell (live versus
dead) variation in adhesion capacity, Studies are needed to determine the e
xtent to which P. gingivalis strain variation is reflected in variation of
other strains in humans.