The first two confirmed cases of type E infant botulism occurred in two 16-week-old girls in Rome, Italy. The original diagnosis for the first patient was intestinal blockage due to an ileocecal invagination, which was treated surgically. Postoperatively, the patient became unresponsive and required ventilatory assistance. A diagnosis of infant botulism was then made. The second infant presented to the same hospital 7 1/2 months later with profound weakness, hypotonicity, mydriasis, and areflexia. This case was recognized as possible botulism at admission. Both cases were confirmed by detection and identification of type E botulinal toxin in stool specimens and in enrichment cultures of those specimens. The toxigenic organisms isolated were quite different from Clostridium botulinum type E. The apparent causative organism in each case resembles Clostridium butyricum but produces a neurotoxin that is indistinguishable from type E botulinal toxin by its effects on mice and by its neutralization with type E botulinal antitoxin.

The apparent causative organism from the only reported case of type E infant botulism was isolated and characterized. Except for its ability to produce type E botulinal toxin, this organism (strain 5262) would be unquestionably identified as Clostridium butyricum. This is the second time an organism resembling a defined Clostridium species other than a member of the C. botulinum group has been implicated in infant botulism. In the 9 years since infant botulism was first described, more than 400 cases have been reported.

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