Ottawa, 27 August – Listeria, the deadly bacteria responsible for 12 deaths in Canada, may have developed a tolerance to cleaning practices at meat processing plants, one of the country's leading microbiologists has said.
The University of Manitoba’s Rick Holley said it is likely that Maple Leaf, the company at the centre of the listeria crisis, uses best practice to ensure the safety of its products, yet failed to detect the deadly bug that has triggered a nationwide alert and one of Canada’s largest ever food recalls.
Holley, who heads an international panel on food safety, said: "Maybe the organism that we're looking at right now in this outbreak might be adapted to some peculiar way to have a higher tolerance to the sanitation activities, to the sanitation agents that are being used. That would be unusual, but it's possible.”
The food safety team based at the Toronto plant where the outbreak is thought to have originated takes 3,000 swabs annually and tests them at the company’s in-house lab. A government inspector also based at the factory did not see anything amiss about Maple Leaf’s safety systems that allowed the listeria to flourish.
Listeria is eradicated by cooking but can live in salt and nitrates, as well as being able to grow in temperatures found in refrigerators.
"We need to look very carefully at the effectiveness of what we consider to be acceptable programs in addressing this particular organism," cautioned Holley.
He added: "Normally, one could expect that such activities would detect the organism, but it will hide anywhere. Where you have a regular maintenance program for equipment combined with a regular sanitation programme, you should be able to cover this off. The problem is the organism is coming in to the plant all the time and it's able under normal circumstances to survive in the meat plant and grow. We know that and Maple Leaf knows it too, and the only thing to address it is to put in place programs that will protect us.”
Holley said the present outbreak is a sign that the listeria bacteria can evade even the best safety systems.
Lynn McMullen, a food microbiologist at the University of Alberta, said that while there is more that can be done, there were limits. What makes the current outbreak unusual is that Maple Leaf is “very good” at food safety management, she said.
"The organism had to be there somehow. It could be in a drain, it could be on a human, it could be any place, but often they target the drains because they'll find them in the drains. How that organism got from a drain to a food product is very difficult to figure out. This is something that is very unusual. It doesn't happen everyday."
But she doubts that if the listeria has developed resistance, it will be of the proportions found in so-called hospital superbugs responsible for MRSA.
McMullen said: "These organisms are everywhere in the environment. They don't need to adapt. The ones at the hospitals are adapting to antibiotic pressure. These guys don't have that kind of pressure. We don't do that in our food processing plants, so it's not a matter of them becoming a superbug in the same sense that the organisms in the hospitals are becoming. They're just a really resistant organism. They always have been, but the processors know how to deal with it, so this is a rare occurrence. I don't have any real quick and dirty, 'Here's what they should have done answers,' because they just don't exist."