VIRULENCE FACTORS OF THE PERIODONTOPATHOGEN ACTINOBACILLUS-ACTINOMYCETEMCOMITANS

ACTINOBACILLUS ACTINOMYCETEMCOMITANS is an important periodontopathoge n that has been implicated in juvenile and adult periodontitis. This c apnophilic coccobacillus elaborates a number of virulence factors such as a bacteriocin, chemotaxis-inhibiting factor, immunosuppressive fac tors, cytotoxic factors, Fc binding proteins, lipopolysaccharide (LPS) , collagenases, antibiotic resistant determinants, adhesins, and invas ins. The adhesins are associated with the bacterial surface or release d into the surrounding environment in the form of vesicles. Adhesion t o epithelial cells involves multiple determinants and is influenced by both bacterial and host environmental conditions. Invasion is a rapid process which occurs within 15 minutes post-infection. Host cell acti n is polymerized around the invading bacteria. Bacteria enter through a membrane-ruffled region of the host cell. This internalization proce ss triggers vesicle formation on the bacteria. A. actinomycetemcomitan s is taken up in a vacuole but is seen free in the cytoplasm in a shor t period of time. The number of internal organisms does not increase w ith time. A. actinomycetemcomitans can transcytose through the epithel ial cells and is released from the host cell in 5 hours. We hypothesiz e that A. actinomycetemcomitans uses invasion of the epithelial cell a s a mechanism to penetrate deeper tissues by cell-to-cell spread.