T. Lilly

Clostridium botulinum Spores in Infant Foods: A Survey

In an examination of 10 categories of infant foods obtained in the Washington, D.C. area, Clostridium botulinum spores were detected in 2 of 100 samples of honey and 8 of 40 samples of corn syrup. This is the first report of the occurrence of C. botulinum spores in retail samples of corn syrup. In an ensuing nationwide survey of corn syrup, C. botulinum spores were detected in 5 of 961 bottles examined.

Outgrowth of Clostridium botulinum in shredded cabbage at room temperature under a modified atmosphere.

The ability of Clostridium botulinum types A and B spores to grow and produce toxin in shredded cabbage at room temperature under a modified atmosphere was investigated. Seven type A and seven type B strains of C. botulinum , mostly of vegetable origin, were used as inocula. Shredded cabbage in high barrier bags, 250 g/bag, was inoculated with various numbers of spores, sealed under a modified atmosphere of 70% CO2 and 30% N2 and incubated at room temperature. Duplicate bags were examined for organoleptic acceptability and the presence of toxin from day 3 by blending the entire contents of each bag and injecting mice with dilutions of the extracts. Toxic extracts were typed with appropriate antitoxins. Only type A spores grew and produced toxin in the cabbage. An inoculum of approximately 100-200 type A spores/g of cabbage, whether in single strains or in various combinations, produced toxin on days 4, 5, and 6, while the cabbage was still organoleptically acceptable, as determined by appearance, odor, and texture.

Incidence of Clostridium botulinum in vegetables packaged under vacuum or modified atmosphere

Because modified atmosphere-packaged (MAP) vegetables may provide an anaerobic environment conducive to Clostridium botulinum growth and toxin production, the incidence of C. botulinum spores in commercially available, precut MAP vegetables was determined. One-pound (454-g) packages of MAP vegetables were aseptically opened, added to freshly steamed and cooled sterile trypticase-peptone-glucose-yeast extract broth and incubated at 35°C for 7 days. Positive and negative controls were included with each sampling. After incubation the broth cultures were tested for toxicity by the standard mouse bioassay. Of the 1,118 MAP vegetable packages examined, one package each of shredded cabbage, chopped green pepper, and Italian salad mix contained C. botulinum type A spores. One additional salad mix (main ingredient, escarole) contained both C. botulinum type A and type B spores. Results indicated a low overall incidence rate (0.36%) of C. botulinum spores in commercially available precut MAP vegetables.

Effect of Low Temperatures on Growth of Clostridium botulinum Spores in Meat of the Blue Crab

The ability of unheated and heated spores of Clostridium botulinum types B. E, and F to grow and produce toxin in crabmeat from the blue crab at low temperatures was investigated. Sterilized crabmeat was seeded with 103 unheated spores/g or 104 heated spores/g and incubated anaerobically at 4, 8, 12, and 26 C. Broth cultures served as controls. Both unheated and heated spores of the three strains grew and produced toxin in crabmeat at 26 C in 3 and 6 days, respectively. In addition, unheated spores of the nonproteolytic type E strain grew and produced toxin in crabmeat at 12 C in 14 days. Neither heated spores of type E nor heated or unheated spores of types B and F grew in crabmeat at any refrigerated temperature within 180 days.

Evaluation of the Botulism Hazard from Nitrogen-Packed Sandwiches

Clostridium botulinum was inoculated into hamburger, sausage and turkey sandwiches, which were subsequently placed in a nitrogen atmosphere. Growth of the bacterium was studied to assess the botulism hazard. Hamburgers inoculated with C. botulinum types A and B and incubated at room temperature became toxic on day 4 while remaining fully acceptable organoleptically. Sausages became toxic on day 7 while appearing marginally acceptable. In air at room temperature, all sandwiches were obviously decomposed before toxin was produced. Refrigeration under nitrogen prevented toxin production by types A and B; however, hamburgers inoculated with type E were toxic at 12 C in 30 days while appearing fully acceptable. All refrigerated sandwiches were either fully or marginally acceptable organoleptically throughout the 60-day observation period; none were obviously decomposed. Turkey sandwiches did not become toxic at any temperature or incubation time studied.

Toxin Production by Clostridium botulinum in Shelf-Stable Pasteurized Process Cheese Spreads

Five non-refrigerated, pasteurized process cheese spreads, considered shelf-stable, were studied for their ability to support growth and toxin production by spores of Clostridium botulinum types A and B. Based on pH and water activity (aw) Cheese with Bacon, Limburger, Cheese Whiz, Old English, and Roka Blue cheese spreads were selected for the study. The pH ranged from 5.05 to 6.32 and the aw from 0.930 to 0.953. Fifty jars of each cheese spread were inoculated with 24,000 spores each; an additional 50 jars of the Cheese with Bacon spread received 460 spores each. The inoculum consisted of five type A and five type B strains in 0.1 ml of 0.85% NaCl. At 35 C, 46 jars of Limburger and 48 jars of Cheese with Bacon spread, which received the greater inoculum, became toxic starting at 83 and 50 days, respectively. One jar of Cheese with Bacon spread which received 460 spores became toxic. The average toxicity of the Limburger was 3000 MLD/ml of extract as compared with 54 MLD/ml for the Cheese with Bacon spread. Results of this study will be considered in determining whether these cheese spread products should be treated as low-acid canned foods under the Good Manufacturing Practice Regulations of the Food and Drug Administration.

Evaluation of the Botulism Hazard in Fresh Mushrooms Wrapped in Commercial Polyvinylchloride Film

The botulism hazard in fresh mushrooms wrapped in commercial polyvinylchloride (PVC) film appears to be minimal. At the end of their normal shelf-life, 1,078 packages of PVC-wrapped mushrooms were all free of botulinum toxin. Since inoculated mushrooms were occasionally found to be toxic (14 in 250 packages) when only one 1/8-inch hole was punched in the wrapper, and none became toxic when two holes were present, it seems prudent to recommend that PVC-wrapped tills of mushrooms have two holes in the wrapper.

Evaluation of unacidified products bottled in oil for outgrowth and toxin production by Clostridium botulinum

A variety of unacidified products bottled in oil or water were investigated for their ability to support growth and toxin production by Clostridium botulinum . The products were inoculated with a mixture of five strains of C. botulinum type A spores (about 50 spores/g or ml) and incubated at room temperature (23°C). At monthly intervals the organoleptic acceptability of the products, as determined by appearance, odor, and texture, was evaluated and a portion of each sample was removed, diluted 1:2 in gel-phosphate buffer, and injected intraperitoneally into mice. At the end of 4 months the drained solids of each sample were macerated with a minimal amount of buffer and centrifuged; the clear extracts were then injected into mice. None of the products tested supported growth and toxin production by C. botulinum .