Differentiation between spores of Bacillus anthracis and Bacillus cereus by a quantitative immunofluorescence technique

Abstract

A quantitative immunofluorescence assay based on fiber optic microscopy was used to measure the reaction of formalized spores of B. anthracis and B. cereus isolates with fluorescein conjugates prepared by hyperimmunization with B. anthracis Vollum spores. The spores of 11 of the 20 B. cereus strains reacted with the anti-anthrax conjugate to such an extent that they were indistinguishable from the several B. anthracis isolates tested. Absorption of the conjugate with spores of B. cereus NTCTC 8035 and B. cereus NCTC 10320 greatly reduced the cross-reaction with the B. cereus preparations so that the mean specific fluorescence of samples of B. cereus spores was in no case higher than 14% of the fluoresence of a reference B. anthracis Vollum preparation. [These results could lead to development of diagnostic reagents for anthrax and to methods for determining the serologic relatedness of B. anthracis and nonanthrax Bacillus spp.].