Food safety: New methods to prevent botulism
Posted: December 30th, 2010 - 3:44pm
Source: Healthy Magination
Guest blogger Dan Ferber is the coauthor, with Paul Epstein, MD, of the upcoming Changing Planet, Changing Health (University of California Press, April 2011), which covers how the climate crisis threatens human health and what we can do about it. His work has appeared in numerous magazines, including Reader’s Digest, Popular Science, Audubon, and Science.
Eggs laced with Salmonella. Spinach with E. coli. Hot dogs with Listeria. News of outbreaks like these, which have appeared regularly in recent years, can make you want to go on a hunger strike. Indeed, the World Health Organization estimates that food borne illness sickens one in three people a year worldwide. But what’s less well known is the progress underway that’s to help make our food supply safer.
Case in point: botulism. Rare but devastating, food borne botulism sickens about 50 people in the United States each year and several thousand worldwide. Botulism begins when dormant forms of the bacterium Clostridium botulinum called spores revive and multiply. This happens most often in canned or salted fish in the United States, says Michael Peck, Ph.D., a microbiologist at the Institute of Food Research in Norwich, U.K. In Europe, Peck says, outbreaks are often associated with sausage; indeed the name of the diseases comes from the Latin botulus, or sausage.
Botulism toxins enter nerves and block them from passing signals to muscles, causing paralysis so severe that victims are often chained to a mechanical respirator for two months while the toxin slowly works its way out of the body. All this makes it critical to accurately, quickly and cheaply detect botulism. But the current gold-standard test was not up to snuff, says immunologist Daniel Douek, MD, PhD, of the National Institute of Allergy and Infectious Diseases.
That lesson hit home for Douek when his five-month-old son was diagnosed with infant botulism. The only test approved by the Centers for Disease Control and Prevention (CDC) required researchers to isolate samples, then send them away to the CDC, where technicians inoculated mice, waited up to five days, and watched which mice died. “The only test that’s approved is expensive, time-consuming, and geographically limited,” Douek says.
Douek, who typically works on AIDS rather than food safety, set out to build a better botulism diagnostic, and eventually developed an inexpensive two-step assay that can be carried out in a matter of hours. C. botulinum produces at least one of seven closely related and extremely potent toxins, and it’s critical to know which varieties of toxins are present because the antidotes to each are different. Douek’s team eventually developed a two-step test that does the trick.
The first step detects the presence of botulism regardless of which of the seven types of neurotoxin it produces. The second step identifies which toxins are present, so that doctors can give the proper antidotes. The method could be used by food processors to test for botulism, and it could also be used to thwart bioterrorism attacks in which terrorists add botulism toxin to the water supply, says Douek. The NIH team reported their work in the journal BioMedCentral Microbiology in October.
Meanwhile, Peck’s team from the Institute of Food Research has also developed a complementary test for botulism that measures levels of the microbes directly in food. The botulism bug, C. botulinum, produces a hardy, dormant form called a spore that survives heat treatment and can grow at refrigerator temperatures. Peck’s team devised a method to detect this dangerous, cold-loving strain of the botulism bug.
First they heated food samples to kill other bacteria, then they grew the samples at temperatures cool enough that only the cold-loving botulism bugs could grow. Then they used a DNA-based method to measure levels of botulism toxin. The test worked on a wide range of prepared foods, and accurately and sensitively detected the more dangerous form of botulism in egg pastas and canned scallops, they reported in Applied and Environmental Microbiology in October. “I think it will help control the food-borne botulism hazard,” Peck says.
Neither of these tests are in widespread use just yet. But both can help us rest a bit easier, knowing that improved food-testing methods could soon help protect people from some of the most devastating cases of food poisoning around.
CONNECT THE DOTS
To learn more, visit the Centers for Disease Control and Prevention, which has a fact sheet on botulism and a fascinating video on the history of the disease, or visit Medline Plus for an overview and tips on how to prevent botulism.