Botulism in Canada--summary for 1997.
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Botulism↗
Biomedical subjects
B Blanchfield
Publications and source records attributed to B Blanchfield.
Effect of pH and CO2 on growth and toxin production by Clostridium botulinum in English-style crumpets packaged under modified atmospheres.
The effect of pH and CO2 on both growth of and toxin production by Clostridium botulinum in English-style crumpets, packaged under modified atmospheres was investigated using a 2 x 2 factorial experiment. English-style crumpets (water activity, 0.990; pH 6.5 and 8.3) were inoculated with C. botulinum spores types A and proteolytic B (500 spores/g), packaged in either 60% CO2 (balance N2) or 100% CO2, stored at ambient temperature (25 degrees C), and monitored daily for toxicity. Toxin was detected after 4 days in crumpets packaged in 60% CO2, irrespective of initial product pH. Toxin production was delayed 1.5 to 3 days in crumpets packaged under 100% CO2. Analysis of variance indicated a significant interaction effect of pH and %CO2 on time of earliest toxin detection. Delay of toxin production was greatest for high pH (8.3) crumpets. All products were organoleptically acceptable at the time of toxigenesis, and therefore, high moisture-high pH bakery products, if contaminated with spores of C. botulinum, could become hazardous if packaged in atmospheres containing CO2.
Atmosphere↗
Growth and toxin production by Clostridium botulinum in English-style crumpets packaged under modified atmospheres.
To determine the safety of a high moisture bakery product, packaged under modified atmospheres, challenge studies were done on English-style crumpets (water activity [a(w)] 0.990, pH 6.5) inoculated postbaking with Clostridium botulinum types A and proteolytic B spores (5 X 10(2) spores/g). Products were packaged either in air, in air with an Ageless FX200 oxygen absorbent, or in a CO2/N2 (60:40) gas mixture, stored at ambient temperature (25 degrees C), and monitored for toxicity daily. All inoculated crumpets were toxic within 4 to 6 days and were organoleptically acceptable at the time of toxigenesis. Counts of C. botulinum increased to approximately 10(5) CFU/g at the time of toxicity. To determine the effect of baking on product safety, subsequent challenge studies were done on crumpets inoculated with 5 x 10(2) spores/g (baked weight basis) prior to baking. All crumpets were toxic after only 6 days, irrespective of packaging conditions, and toxigenesis again preceded spoilage. Temperature profile studies showed that the maximum internal temperature reached during baking was 97 degrees C, and the total baking process was equivalent to 0.03 min at 121 degrees C. The actual time to toxin production in both studies (4 to 6 days) correlated well with the predicted time (3.4 days) using the U.S. Department of Agriculture Pathogen Modeling Program (version 5.1) for proteolytic strains of C. botulinum. These studies confirm that high moisture bakery products, if contaminated with C. botulinum spores either pre- or postbaking, could pose a public health hazard, if packaged in air (in a high gas barrier package where O2 was depleted and CO2 was generated during storage) or under modified atmosphere packaging conditions and stored at ambient temperature.
Botulinum Toxins↗
Growth and toxin production by Clostridium botulinum on inoculated fresh-cut packaged vegetables.
To determine the safety of fresh-cut vegetables packaged in modified atmosphere, challenge studies using both nonproteolytic and proteolytic strains of Clostridium botulinum were performed with a variety of fresh-cut packaged salads and vegetables stored at different temperatures. When vegetables were inoculated with spores of C. botulinum and incubated in low-O2 atmospheres, spore germination and growth and toxin production were observed. Botulinum toxin was produced by proteolytic types A and B on onion, butternut squash, rutabaga, salad, and stir-fry vegetables. Nonproteolytic C. botulinum produced toxin on butternut squash and salad. Nonproteolytic C. botulinum was capable of producing neurotoxin at temperatures as low as 5 degree C whereas proteolytic strains produced neurotoxin at 15 degrees C and higher. Although most samples were visibly spoiled before detection of botulinum toxin, samples of butternut squash and onion remained acceptable after detection of toxin. The strict maintenance of low temperatures (< 5 degrees C) is recommended in order to control the potential growth of C. botulinum on fresh-cut vegetables packaged in a modified atmosphere.
Botulinum Toxins↗
Effect of avian intestinal microflora possessing adhering and hydrophobic properties on competitive exclusion of Salmonella typhimurium from chicks.
The role of adherence and hydrophobic properties of native gut microflora in competitive exclusion of salmonellas from chicks is reported. Pure bacterial strains were isolated from washed caeca of 3-d-old chicks which had been treated on the day of hatch with a microflora from salmonella-free adult birds. These strains, when added to known mixtures of pure cultures, improved the efficacy of the mixtures in protecting chicks against a challenge of 10(5) cfu of Salmonella typhimurium. Strains from washed caeca and from other sources were also screened for hydrophobic properties. Undefined microflora and strains freshly isolated from washed caeca and which were hydrophobic improved the efficacy of protective mixtures, while none of the combination of hydrophobic strains obtained from stored strains had any beneficial effect.
Animals↗
Protection of chicks against Salmonella infection with a mixture of pure cultures of intestinal bacteria.
A mixture of 28 pure cultures was prepared from the organisms isolated from native gut microflora (fecal and cecal contents) of adult Salmonella-free birds. This mixture was orally administered to 1-day-old chicks and examined for its efficacy against challenge with 10(5) colony-forming units of nalidixic-acid-resistant Salmonella typhimurium in six consecutive trials during a 20-month period. The efficacy of the mixture, which was prepared for each trial from stored isolates, progressively decreased, while that from stored fecal content remained unimpaired. Twenty-three cultures in the mixture were tentatively identified as belonging to seven different genera; the genus of the five other cultures remained unknown.
Animals↗