Pathogenicity of anaerobic bacteria

The pathogenicity of anaerobic bacteria has become better understood during the last decade. In addition to the relatively well characterized exotoxins of histotoxic clostridia, a number of factors involved in the production of disease have been described in Bacteroides and other anaerobic bacteria. Important factors are particularly superoxide dismutase, catalase, the abscess inducing capsular polysaccharide of Bacteroides fragilis, proteases, lipases, heparinase, and nucleases. Resistance against phagocytosis has been described in Gram-negative species. Pathogenicity factors like hyaluronidase, haemolysin, lipolysins, and neuraaminidase have been isolated even in species such as the propionibacteria, which are considered to have a low pathogenicity. The ability of different strains to enhance the manifestations of infections when they occur together has pointed to a colloboration between their individual pathogenicity factors in the sense that they enhance the activity of each other. The ability of anaerobes to produce enzymes inactivating antibiotics has become well established and is an important factor in the maintenance of an infection during therapy.