Superbug found in food troubles scientists
Saskatchewan researchers discover first antibiotic-resistant bacteria in seafood
The spread of antibiotic-resistant bacteria could be wider than previously thought, say University of Saskatchewan researchers who discovered the organism in a frozen squid purchased in Saskatoon.
It’s the first instance of finding antibiotic-resistant bacteria in food, says Western College of Veterinary Medicine assistant professor Joe Rubin, who co-authored a study published in the Centre for Disease Control journal Emerging Infectious Diseases.
“While this certainly is a troubling finding, we don’t know how widespread these organisms are in these niche market food products or how they got there, so expanding our surveillance programs is our best next step to address these questions,” Rubin said.
The discovery: Researchers bought several items from a Chinese grocery store in Saskatoon. They found a bacteria called Pseudomonas, which produces an enzyme called carbapenemase, in a frozen squid believed to be imported from South Korea.
“The carbapenemases allow bacteria to be resistant to the most commonly used and last-line-ofdefence drugs we have for treating infections in people,” Rubin said.
“If we see increasing resistance to these compounds, it’s a really serious threat to public health. We want to make sure we don’t have untreatable infections.”
The concern: It’s not one kind of bacteria that worries researchers — it’s the transmission of the genes between different kinds of bacteria that could be a problem.
“Bacteria can share DNA with each other,” Rubin said. “They can swap pieces of DNA and express those genes. The real problem is that these genes are potentially available to pathogenic bacteria that may be more likely to cause disease.”
The Pseudomonas that researchers found is not a common cause of disease, but it could be a problem for people with impaired immune systems.
“The real concern is that if somebody was to eat this organism and it was to get into the gastro-intestinal tract, it might share those resistance genes with other bacteria in there,” Rubin said. “Maybe the gene goes into an E. coli and causes a urinary tract infection which is resistant to treatment.”
The histor y: Warnings about “superbugs” are increasing, as is the attention from the international medical community. The CDC estimates the infections kill 23,000 U.S. residents every year.
“Until very recently, and it’s still largely the case, the biggest risk factor was travel history, so people who’ve travelled to areas where these resistance organisms are much more common,” Rubin said.
“We’re also seeing hospital outbreaks. What we’re worried about with this finding is that now we’re expanding the potentially exposed segment of the population. It’s not just if you’ve travelled or been hospitalized, it might be people purchasing certain products from the grocery store.”
The safety: Rubin doesn’t want to scare people away from eating seafood or other potentially contaminated food. The best defence is smart food preparation, he said.
“People need to continue to be vigilant with food hygiene. Transmission can be prevented by making sure we don’t cross-contaminate raw meat and ready-to-eat food,” Rubin said. “We need to use different cutting boards, make sure we’re washing hands and cleaning kitchen surfaces and making sure food is cooked to a proper internal temperature.”
Researchers aren’t sure how the bacteria got into the squid.
“Potentially it picked it up from its environment; maybe it was cross contamination during processing or shipping or cross contamination at the retail level,” Rubin said. “There are complexities that have yet to be investigated.”
The next step: These are early findings, and Rubin plans to do more research. “That’s where we are going — trying to identify what the risk is to human health,” he said. “Is it just an interesting and incidental finding, or does it have some real implications?
Rubin is working with federal public health scientists to develop a strategy to determine how widespread the organisms are and how they are entering the food chain. The first step is a study with samples from across Canada from different locations. “We need to know if we’re dealing with a larger phenomenon or an isolated incident so we can develop some intervention strategies,” he said.