VIRULENCE FACTORS IN ANAEROBES

Among the broad spectrum of species of anaerobic bacteria in the norma l flora of humans, a few exhibit marked pathogenic potential and are r esponsible for the majority of infections. The factors that determine the virulence of particular species are varied and probably interrelat ed. Just as most anaerobic infections are polymicrobial and depend on interactions of a combination of species, the virulence of a species p robably depends on a combination of properties, including surface stru ctures, metabolic functions, ability to avoid the host's defenses, and capacity to damage tissues. Thus, the production of each virulence fa ctor-adhesins that attach to epithelial and red blood cells and to oth er bacteria, producing metabolically interdependent ecosystems; capsul es that protect against phagocytosis and induce abscess formation; lip opolysaccharide; proteases, including those that degrade immunoglobuli ns and complement components; and other hydrolytic enzymes-represents only a component of virulence, but a consideration of these factors in combination begins to clarify the mechanisms by which anaerobes cause disease.