ERS obtained from Staph. aureus by mild extraction with physiologic saline solution possess activity of inducing nonspecific opsonins which react with homologous bacteria and with related Gram-negative bacteria. ERS from Staph. aureus weakly stimulated precipitins and antibodies active in passive hemagglutination and induced a marked rise in agglutinin titers especially for the homologous strain and Gram-negative S. typhimurium bacilli. N-acetyl-D-glucosamine absorbed the opsonizing factor for various bacteria with heterologous activity.
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