Proteolytic activity of selected clinical isolates of Serratia marcescens against human serum proteins.

Six representative clinical isolates of Serratia marcescens were examined for proteolytic activity against various proteins of normal fresh human serum. The extent of proteolytic activity was screened with micro-scale immunoelectrophoresis and quantitatively documented with the aid of Laurell's rocket electroimmuno assay. The 6 S. marcescens strains regularly altered, albeit to varying degrees, complement components C3a, C3c, C4, C5, and C9, and haptoglobin. Apolipoprotein and immunoglobulin A, the latter derived from human colostrum, were attacked by 5 and 4 isolates, respectively. Two isolates altered alpha 1-antitrypsin, whereas only one isolate interacted with alpha 2-macroglobulin and transferrin. In contrast, alpha 2-HS-glycoprotein, alpha 1-antichymotrypsin, and serum IgA, IgG, and IgM immunoglobulins were not affected by the test strains.