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Food

Are America's Onions Infecting Australia with a Deadly Superbug?

An Australian researcher claims to have discovered a link between a rise in cases of Clostridium difficile and imports of onions from the United States.
Photo via Flickr user Dubravko Sorić

Just when you thought you could play it fast and loose with kitchen hygiene, along comes a tale of a superbug that can quite literally make you crap your pants to death.

Clostridium difficile (commonly known as C. diff) is aptly named. A hard-to-treat bacteria, it can be resistant to many antibiotics and often results in infectious diarrhea that can turn fatal. Just last week, the Centers for Disease Control released a new study that found that C. diff. sickened 453,000 Americans and caused 29,000 deaths in 2011 alone.

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Like many foodborne pathogens, C. diff is frequently spread through the fecal-oral route (which is exactly what it sounds like). In this case, however, the vector isn't an unwashed finger or a dirty chicken breast: It's onions.

That's the theory, at least. Thomas Riley, a professor of microbiology at the University of Western Australia, told the Daily Telegraph he believes that a recent uptick in C. diff cases in Australia could be linked to onions from the US.

"[There] had to be a common source, and the most likely source is food," Thomas told the paper. "We overlayed imports of onions at the time for this particular bug and it [the genome] was a perfect match."

Thomas said that he will detail his findings in an upcoming report that demonstrates a possible link between onion imports and the rise of C. diff infections.

C. diff frequently arises in hospitals or nursing homes—where widespread broad-spectrum antibiotic use leaves patients' healthy gut flora weakened and vulnerable—and most often infects the elderly and people with weakened immune systems. But there is cause for concern that C. diff could in fact be a foodborne pathogen, even though no cases of foodborne illness definitively linked to C. diff have been reported to date.

A Scottish study from 2009 analyzed 40 ready-to-eat salads for C. diff, and found that three of them tested positive; another study from 2007 found that 20 percent of the Canadian ground beef it sampled was positive for C. diff.

Yet another study from 2012 concluded that C. diff can be found in meat, seafood products, and in vegetables. "Foods that are ready to eat or that we typically eat raw are more likely to be a problem," said Alex Rodriguez-Palacios, a food scientist and co-author of the study, at the time. "But we also know that a small number of food animals have C. diff at the time of slaughter. There are now recent indications of food contamination during processing."

The onions could potentially become carriers of C. diff if they're fertilized with infected manure. The problem is that border patrols don't typically check for the presence of C. diff. Even worse, conventional washing and cooking doesn't always destroy the bacteria.

In the meantime, there's not much to do but await the publication of Thomas's study—and maybe start stocking up on probiotics.