The fluorescent antibody test for the identification of strains of Clostridium botulinum type E

Abstract

A fluorescent antibody test for the identification of toxigenic and nontoxigenic type E strains of C. botulinum is described. Hyperimmune rabbit sera were prepared to cell suspensions of the D8, 070, and Beluga strains and to spores of the D8 and PM-15 strains. Fluorescein isothiocyanate immunoglobulin conjugates were prepared and absorbed with C. bifermentans and diluted to eliminate non-specific staining and cross-reactivity with related serotypes. Enzyme pretreatment of spores and washing the stained spores in carbonate buffer, pH 9.0, enhanced the sensitivity of the test. Conjugates of cell antiserum, in most cases, stained the spore bodies and not the vegetative cells of the cross-reacting strains. Conjugates of spore antiserum stained vegetative cells as well as spores but the fluorescence of the cells was eliminated by absorption of the conjugates with young cells of the homologous strain. The absorbed conjugates stained spores of 19/20 isolates from diverse geographical areas without any reduction in the intensity of fluorescence, indicating that spore antigens carry the determinant groups of type E specificity and that the common antigen is a component of the spore body. In addition, some of the cross-reacting strains showed the same degree of fluorescence as the homologous strain, suggesting that more than one antigen may be shared by these strains.