CHARACTERIZATION OF THE DERMONECROTIC TOXIN IN MEMBERS OF THE GENUS BORDETELLA

All members of the genus Bordetella and Pasteurella multocida (a gram- negative bacillus genetically unrelated to Bordetella spp., yet often sharing the same ecological niche) produce a dermonecrotic toxin (DNT) . The amount of toxin produced and the time required for appearance of the lesions are identical for Bordetella pertussis, B. parapertussis, and B. bronchiseptica but different for P. multocida and B. avium. DN T has been reported to act by promoting vasoconstriction; however, vas oactive compounds (verapamil, prazosin, hydralazine, tolazoline, or is oxsuprine) are able to reverse the action of the toxin only slightly. Vasoconstrictors (atropine, serotonin, epinephrine, or endothelin) did not produce DNT-like lesions. We have characterized a region of DNA e ssential for DNT expression. We have determined by Southern analysis t hat the restriction map of the DNT gene is nearly identical in B. pert ussis, B. parapertussis, and B. bronchiseptica, but the sequences are not present in toxigenic B. avium and P. multocida strains. A gentamic in resistance-origin of transfer cassette cloned into a 1.8-kb NotI-Ba mHI fragment results in constructs which can be mobilized and recombin ed into the Bordetella chromosome, rendering the resultant B. pertussi s, B. parapertussis, and B. bronchiseptica strains negative for DNT. A 5-kb BamHI-ApaI fragment from the B. pertussis chromosome was sequenc ed and revealed homology to the Escherichia coli CNF1 (cytotoxic necro tizing factor 1) toxin.