IMMUNOFLUORESCENCE AMONG STRAINS OF CLOSTRIDIUM BOTULINUM AND OTHER CLOSTRIDIA BY DIRECT AND INDIRECT METHODS

Abstract

SUMMARY Immunofluorescence among strains of Clostridium botulinum and other clostridia, using somatic antisera, was studied by both direct and indirect methods. The 30 toxigenic type E strains, as well as all nontoxigenic variants and all nonproteolytic type B and F strains tested, fluoresced brilliantly with all type E antisera. Similarly, all type E and the nonproteolytic type B and F strains fluoresced with the nonproteolytic type B and F antisera. None of these antisera gave fluorescence with the proteolytic strains of types A, B and F, but the proteolytic strains cross‐reacted as a separate group. Nonproteolytic antisera did not fluoresce with other clostridia. Proteolytic antisera fluoresced with Clostridium sporogenes, Clostridium tetani and Clostridium histolyticum, but this varied with the antiserum. In indirect tests, absorbed antisera showed homologous fluorescence to be specific, and cross‐reactions with C. botulinum strains to be due to common antigens. Proteolytic antisera absorbed with C. sporogenes had little or no loss of fluorescence for C. botulinum, whereas fluorescence with C. sporogenes was removed. Blocking tests of conjugates of these antisera gave similar results. Fluorescence was less bright in the direct test than the indirect, but the direct test was quicker, gave less background and nonspecific staining and resulted in fewer undesirable cross‐reactions; therefore, the direct test seems better adapted to screening for C. botulinum in foods and environmental samples. Fluorescence of nontoxigenic variants, however, may be a complicating factor by either method.