MODELS OF INVASION OF ENTERIC AND PERIODONTAL PATHOGENS INTO EPITHELIAL-CELLS - A COMPARATIVE-ANALYSIS

Bacterial invasion of epithelial cells is associated with the initiati on of infection by many bacteria. To carry out this action, bacteria h ave developed remarkable processes and mechanisms that co-opt host cel l function and stimulate their own uptake and adaptation to the enviro nment of the host cell. Two general types of invasion processes have b een observed. In one type, the pathogens (e.g., Salmonella and Yersini a spp.) remain in the vacuole in which they are internalized and repli cate within the vacuole. In the other type, the organism (e.g., Actino bacillus actinomycetemcomitans, Shigella flexneri, and Listeria monocy togenes) is able to escape from the vacuole, replicate in the host cel l cytoplasm, and spread to adjacent host cells. The much studied enter opathogenic bacteria usurp primarily host cell microfilaments for entr y. Those organisms which can escape from the vacuole do so by means of hemolytic factors and C type phospholipases. The cell-to-cell spread of these organisms is mediated by microfilaments. The investigation of invasion by periodontopathogens is in its infancy in comparison with that of the enteric pathogens. However, studies to date on two invasiv e periodontopathogens, A. actinomycetemcomitans and Porphyromonas (Bac teroides) gingivalis, reveal that these bacteria have developed invasi on strategies and mechanisms similar to those of the enteropathogens. Entry of A. actinomycetemcomitans is mediated by microfilaments, where as entry of P. gingivalis is mediated by both microfilaments and micro tubules. A, actinomycetemcomitans, like Shigella and Listeria, can esc ape from the vacuole and spread to adjacent cells. However, the spread of A. actinomycetemcomitans is linked to host cell microtubules, not microfilaments. The paradigms presented establish that bacteria which cause chronic infections, such as periodontitis, and bacteria which ca use acute diseases, such as dysentery, have developed similar invasion strategies.