Rather than releasing into extracellular space, Porphyromonas gingivalis might spread directly from one cell to the next, say researchers in the January issue of the journal Infection and Immunity.
P. gingivalis successfully invades, multiplies in and survives for extended periods in primary gingival epithelial cells. It has been unknown, however, whether P. gingivalis resides in the cytoplasm of infected cells throughout the infection or can spread to adjacent cells over time.
A research team led by Özlem Yilmaz, Ph.D., research associate, University of Washington, Seattle, discovered that P. gingivalis "translocates" directly into neighboring cells.
The team developed a technique based on flow cytofluorometry and fluorescence microscopy to study the propagation of P. gingivalis at different stages of primary gingival epithelial cell infection. They found that P. gingivalis spread from cell to cell and that the amount of spreading increased gradually over time. There was a low level of propagation of bacteria to uninfected cells early in the infection (three hours), but there were 20-fold and 45-fold increases in the propagation rate after 24 and 48 hours, respectively.
Using immunofluorescence microscopy, researchers discovered that intercellular translocation of P. gingivalis may happen via a protrusion of the cell membrane, which appears to be composed of the filament-like actin protein. This allows the bacterium to colonize oral tissues without exposing itself to antibody-producing immune cells.
This study was funded by a grant from the National Institute of Dental and Craniofacial Research.
