ABSTRACT
Postbum Immunity and Infection 233
croorganisms influence the course of infection. For instance, to produce a pustule in volunteers, an intradermal or subcutaneous injection of about 7.5 x 106 Staphylococcus aureus is required (53,54). Cell walls of several strains of S. aureus contain peptidoglycan, a mucopeptide that mimics endotoxin, can activate both the classic and alternate complement pathways, and elicit cell-mediated immunity (55). An intradermal injection of staphylococcal peptidoglycan in experimental animals inhibits leukocyte migration and edema accumulation at the injection site, and thus facilitates localized abscess formation (56). Surface-associated exopolysaccharide, or slime (57), is a virulence factor associated with some staphylococci and many gram-negative organisms, which impairs phagocytosis and inhibits neutrophil (58) catalase activity and thus protects the bacteria against PMN -induced lethal oxidant injury.
