An immunoassay for the rapid and specific detection of three sialidase-producing clostridia causing gas gangrene

A rapid and methodologically unusual diagnostic test was developed for the specific detection of Clostridium perfringens, C. septicum and C. sordellii, which cause clostridial myonecrosis. Sialidases (EC 3.2.1.18) secreted by these bacterial species were bound to polyclonal antibodies raised against the respective enzyme and immobilized onto microtiter plates. The activity of bound sialidase was determined with the fluorogenic substrate 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid. The assay permits the detection of a minimum sialidase activity of about 0.1-1 mU/ml of sample solution within 2 h. The sensitivity of the test was reduced by about three-fold for sialidase activities in samples containing 50% serum. Only a few, low cross-reactivities, which never exceeded 10% of the homologous reaction, were observed with 12 sialidases from other bacterial sources. Clinical isolates of the three clostridial species were analysed by this assay and gave positive signals in the homologous test. The assay for the detection of C. perfringens was applied to nine samples from patients suspected to be suffering from clostridial myonecrosis. There was a high correlation between the results of the immunoassay and the bacteriological analysis of infection.