An outbreak of type A botulism associated with a commercial cheese sauce

BACKGROUND

Although botulism is rare, recognition of a possible case of this illness represents a public health emergency. To prevent more cases, prompt investigation must be done to determine whether illness is linked to commercial product or restaurant. Botulism can masquerade as other illnesses, and seemingly unlikely foods can harbor botulinum toxin.

OBJECTIVE

To confirm the diagnosis and determine the cause and extent of an outbreak of botulism associated with food served at a delicatessen.

DESIGN

Retrospective cohort study of patrons of the delicatessen; laboratory analysis of food, serum samples, and stool samples; and traceback of implicated food.

SETTING

Community in Georgia.

PARTICIPANTS

Patrons of the delicatessen.

MAIN OUTCOME MEASURES

Botulinum toxin in food, serum, or stool and Clostridium botulinum in food and stools.

RESULTS

8 of 52 patrons (15%) met the case definition for botulism. In 4 of the 8 patrons, and illness other than botulism was initially diagnosed. Five of the 8 were hospitalized, and 1 died. Stool cultures from 4 patrons yielded type AC. botulinum, and two serum samples contained botulinum toxin. All ill persons ate food from the delicatessen on 1 October 1993. Of the 22 persons who ate at the delicatessen that day, all 8 ill persons but none of the 14 well persons ate a potato stuffed with meat and cheese sauce. An open can of cheese sauce contained type A botulinum toxin and yielded C botulinum on culture. Cheese sauce experimentally inoculated with C botulinum spores became toxic after 8 days at a temperature of 22 degrees C (room temperature).

CONCLUSIONS

A commercial, canned cheese caused a botulism outbreak. This product readily becomes toxic when contaminated by C botulinum spores and left at room temperature. Mild botulism caused by unusual vehicles may be misdiagnosed. Botulism should be included in the differential diagnosis of persons with signs or symptoms of acute cranial nerve dysfunction.

Four ribose 2'-hydroxyl groups essential for catalytic function of the hairpin ribozyme

The hairpin ribozyme catalyzes site-specific cleavage of an RNA substrate using a magnesium-dependent transphosphorylation mechanism. Here, we describe experiments designed to test the importance of ribose 2'-hydroxyl groups for ribozyme function. Ribozymes for this work were synthesized in two segments using solid-phase RNA phosphoramidite chemistry. 2'-Deoxyribonucleotides were systematically introduced at each of the 50 positions within the ribozyme, and the catalytic activity of the resulting mixed RNA-DNA polymers was measured. Deletion of the 2'-hydroxyl group at each of four sites (A10, G11, A24, and C25) was found to result in severe inhibition of cleavage activity (kcat/KM decreased by 100- to 1000-fold), although KM measurements and mobility-shift assays showed that substrate binding was not affected. Identical results were obtained upon substitution of these ribonucleotides with 2'-O-methyl derivatives. Inhibition by 2'-modified sugars at G11 or A24 was rescued by increased Mg2+ concentrations, suggesting that these 2'-hydroxyls may function in magnesium binding. Our results demonstrate that the 2'-hydroxyl groups at A10, G11, A24, and C25 provide essential functions for catalysis, possibly forming important tertiary contacts or magnesium coordination sites that are necessary for active site architecture.