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ABSTRACTBacillus cereusis ubiquitous in nature, and while most isolates appear to be harmless, some are associated with food-borne illnesses, periodontal diseases, and other more serious infections. In one such infection, B. cereusG9241 was identified as the causative agent of a severe pneumonia in a Louisiana welder in 1994. This isolate was found to harbor most of the B. anthracisvirulence plasmid pXO1 (13). Here we report the characterization of two clinical and one environmental B. cereusisolate collected during an investigation of two fatal pneumonia cases in Texas metal workers. Molecular subtyping revealed that the two cases were not caused by the same strain. However, one of the three isolates was indistinguishable from B. cereusG9241. PCR analysis demonstrated that both clinical isolates contained B. anthracispXO1 toxin genes. One clinical isolate and the environmental isolate collected from that victim's worksite contained the cap A, B, and Cgenes required for capsule biosynthesis in B. anthracis. Both clinical isolates expressed a capsule; however, neither was composed of poly-d-glutamic acid. Although most B. cereusisolates are not opportunistic pathogens and only a limited number cause food-borne illnesses, these results demonstrate that some B. cereusstrains can cause severe and even fatal infections in patients who appear to be otherwise healthy.

We have generated more than 100 transgenic alfalfa plants, via Agrobacterium-mediated gene transfer, from genotypes se-lected from five alfalfa cultivars. These plants express the genes for kanamycin resistance and for the coat protein of al-falfa mosaic virus (AMV). The strongest expressers accumulated nearly 500 ng coat protein per mg soluble leaf protein. AMV inoculation of protoplasts from these strong expressers indicated that they were resistant to infection by AMV, while protoplasts from plants containing about a hundred-fold less coat protein and from control untransformed plants were not. Transgenic alfalfa plants containing large amounts of coat protein were, likewise, resistant to AMV. These plants did not develop systemic infections following in-oculation with up to 50 μg/ml AMV, while inoculated control plants developed systemic infections following inoculation with as little as 10 μg/ml AMV. These results demonstrate that expression of the AMV coat protein gene confers resistance to AMV infection in transgenic alfalfa plants.