Coagglutination and enzyme capture tests for detection of Escherichia coli β-galactosidase, β-glucuronidase, and glutamate decarboxylase

Abstract

Polyclonal antibodies to Escherichia coli β-galactosidase, β-glucuronidase, and glutamate decarboxylase were used in coagglutination tests for identification of these three enzymes in cell lysates. Enzyme capture assays were also developed for the detection of E.coli β-galactosidase and β-glucuronidase. The enzymes were released by using a gentle lysis procedure that did not interfere with antibody-enzyme interactions. All three enzymes were detected in 93% (51 or 55) of the E.coli tested by coagglutination, only four nonspecifically agglutinated either two or three of the anti-enzyme conjugates. Thirty-two (76%) non-E.coli isolates were negative by coagglutination for all three enzymes. The enzyme capture assay detected the presence of β-galactosidase in seven of eight and β-glucuronidase in all eight strains of E.coli tested. Some strains of β-galactosidase-positive Citrobacter freundii and Enterobacter cloacae were also positive by the enzyme capture assay, indicating that the antibodies were not entirely specific for E.coli β-galactosidase; however, five other gas-positive non-E.coli isolates were negative by the enzyme capture assay. The coagglutination tests and enzyme capture assays were rapis and sensitive methods for the detection of E.coli β-galactosidase, β-glucuronidase, and glutamate decarboxylase.