Immunoreactivity of 80-kDa peptidoglycan and teichoic acid-like substance of slime producing S. epidermidis and specificity of their antibodies studied by an enzyme immunoassay.

S. epidermidis is considered an important cause of nosocomial bacteraernia in immunocompromized hosts as well as the commonest agent of sepsis in patients with prosthetic devices. Pathogenesis is attributed to adherence and growth on bioniaterials facilitated by production of extracellular slime. The major macromolecules of slime are: a 20-kDa acidic polysaccharide (20-kDa PS) comprising the 60% of carbohydrate-containing slime macromolecules, a peptidoglycan with average molecular size of 80-kDa (30% of slime dry weight) and cell wall teichoic acid-like substance. In this study, antibodies to these macromolecules as well as crude slime were raised in rabbits and their immunological reactivity and specificity were studied by an enzyme immunoassay. All isolated macromolecules induced the production of specific antibodies. 20-kDa PS was less immunogenic than 80-kDa peptidoglycan and teichoic acid-like substance. However, 20-kDa PS was the most potent inhibitor of the reaction of slime with its homologous antibodies revealing that this polysaccharide is the major antigenic determinant of slime. All three antibodies specifically recognize (p < 0.05) and react with slime-producing S. epidermidis in comparison to other staphylococci species. Obtained results indicate that the 20-kDa PS may be distributed in the surface of the slime exposing most of its antigenic determinants to the immune system, whereas those of 80-kDa peptidoglycan and teichoic acid-like substance seem to be less accessible.