From time to time, my daily Recalls and Alerts post includes a warning from the Québec (Canada) Ministry of Agriculture, Fisheries and Food that a “preserved” food – typically a sauce or soup – should not be consumed, because it was improperly processed or stored, and could present a risk of botulism.

This risk is not far-fetched. CDC has just released the following short report on two recent cases of botulism in the USA. Please navigate to the full report for a list of the authors and the background literature.

Notes from the Field: Botulism Caused by Consumption of Commercially Produced Potato Soups Stored Improperly — Ohio and Georgia, 2011

In January and April 2011, CDC provided antitoxin for treatment of two persons with toxin type A botulism associated with consumption of potato soup produced by two companies. On January 28, 2011, an Ohio resident, aged 29 years, was hospitalized after 5 days of progressive dizziness, blurred vision, dysphagia, and difficulty breathing. The patient required mechanical ventilation and botulism antitoxin. On January 18, he had tasted potato soup from a bulging plastic container, noted a bad taste, and discarded the remainder. The soup had been purchased on December 7, 2010, from the refrigerated section of a local grocer, but it had been kept unrefrigerated for 42 days. He was hospitalized for 57 days and then was transferred with residual weakness to a rehabilitation facility.

On April 8, 2011, a Georgia resident, aged 41 years, was hospitalized after 4 days of progressive dizziness and dysphagia. The patient developed respiratory distress, required mechanical ventilation, and was treated with botulism antitoxin. On April 3, she had tasted potato soup purchased from a local grocer, noted a sour taste, and discarded the remainder. The soup, stored in a plastic container labeled “keep refrigerated” in letters 1/8 inch tall, had been purchased on March 16, but had been left unrefrigerated for 18 days. She was hospitalized for 16 days and then was transferred with residual weakness to a rehabilitation facility.

Botulism is caused by a paralyzing toxin produced by Clostridium botulinum bacteria. C. botulinum spores are present in soil and can be found on raw produce, especially potatoes and other root vegetables (1). If a low-acid food such as potato soup is stored unrefrigerated in an anaerobic environment (e.g., a sealed container), without a barrier to bacterial growth, spores can germinate, resulting in bacterial growth and botulinum toxin production (2). Because heating food to a temperature of 185°F (85°C) for 5 minutes inactivates the toxin, proper preparation also is an important safeguard (3).

Improper storage has been documented in previous botulism outbreaks associated with commercially produced, chilled foods. Since 1975, 19 U.S. botulism cases were linked to six such products. Demand for prepared, chilled foods is increasing (4). Labels advising refrigeration might be ignored or not noticed, and do not warn about the danger of consuming unrefrigerated food. The Food and Drug Administration is reexamining labeling requirements. Storage at an improper temperature also can occur before products reach consumers (5). To inhibit the growth of C. botulinum and other microbes, an acidifying agent or other microbial inhibitor, such as citric or phosphoric acid, can be added to prepared, chilled foods before they are sealed in a package. This procedure was used successfully to reduce the danger of botulism from commercial garlic-in-oil products after two outbreaks (6).

Most people think of botulism as a home-canning risk. It’s rare that a commercial “preserved” product is the source of a case of botulism.

In the two cases just published by CDC, the foods – even though displayed in a refrigerated case and/or labeled “keep refrigerated” – the consumer stored their containers of potato soup unrefrigerated for weeks. Both consumers compounded their storage error by tasting the cold soup, even though the container was bulging in one instance.

This is one incident that can be chalked up strictly to the carelessness of a couple of complacent consumers.