E. coli a virulent bacteria | Food safety protocols, safety training critical at every point of production
It takes only 10 to 100 E. coli O157:H7 bacteria to cause serious disease or even death, say microbiologists.
“E. coli is one of the most virulent pathogens we know. Ten cells can cause illness,” said Keith Warriner, a microbiologist at the University of Guelph, Ont., who researches food safety and serious pathogens such as E. coli.
The bacteria occurs naturally in the intestines of mammals such as cattle, which are not affected.
There are hundreds of strains of E. coli and most are harmless. However, the more dangerous strain produces toxins responsible for severe illness and death in humans.
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There are six strains in this family, and Canadians are most familiar with O157. However, Warriner is leading a project to measure the prevalence of all six in cattle. A similar study has been completed in the United States, where the populations were higher than expected.
The O157 strain was identified in 1981 and is a single cell, rod shaped bacterium that can multiply every 20 minutes in the right conditions, said Andrew Potter, director and chief executive officer of the Vaccine and Infectious Disease Organization in Saskatoon. He worked with scientists at the University of British Columbia to develop the first licensed E. coli vaccine. It was later commercialized through Bioniche Life Sciences Inc. in Belleville, Ont.
Adoption of the vaccine was not high because it required three doses and was expensive. Scientists continue to look for an improved product.
It is a tough bacterium, growing best in temperatures of 37 to 39 C. Freezing does not kill it.
“These things can survive for long periods of time on surfaces in the (processing) plant or in the kitchen or in the ground, whether it is cold or hot,” Potter said.
Scientists are researching approaches to killing the bacteria with improved sanitation or bacteriophages.
Phages are viruses that infect and kill specific bacteria. They can be sprayed on the hides of live cattle before they enter the kill plant.
All federal food plants have hazard analysis critical control points plans to prevent contamination.
“The trouble is HACCP plans takes years to develop and cost God knows how much money to implement and if you don’t follow the instructions, you might as well have not spent the money at all,” Warriner said.
Employees need to be trained regularly so they feel responsible for what happens on the manufacturing chain.
Steam pasteurization is semi-effective against bacteria, but processors often don’t apply the steam long enough for fear it might cook the outside layer of the carcass.
Carcasses are also subjected to acid rinses, steam vacuums and visual inspections to make sure no dirt is on the outside that may escape inside to the meat and cause contamination.
In the case of XL Foods, which was closed because of E. coli contamination, the first problem was found in trim, which is off cuts of meat. Trim may not receive additional treatments.
“If we said no more trim in the human food chain, the price of beef would just skyrocket because it really does contribute significantly to the economics of beef processing,” Warriner said.
Nevertheless, getting rid of E. coli, salmonella and listeria should be part of a facility’s food safety culture. Many meat plants experience high turnover, so effective training and supervision is constantly needed.
Education starting at the farm is also valuable, said Joyce Van Donkersgoed, a feedlot veterinarian and epidemiologist in southern Alberta who has researched the pathogen.
“We don’t have good interventions at this point on the farm that are practical and cost effective,” she said.
She is a strong advocate of HACCP and strengthening procedures from the farm to the plant to the consumer because everybody has a responsibility to reduce the risks.
“There is bacteria in the manure of all livestock, whether it is chickens, pigs or cattle,” she said.
“You have to have a HACCP process in place which is designed with critical control points to reduce the risk. You are never going to eliminate them because these are commensal bacteria in cattle, but we can do a lot of things at the processing end and even in the consumer end.”
People have been taught to cook chicken and pork thoroughly, but too often beef is not cooked sufficiently. Cross contamination also occurs when people use the same cutting boards, knives and plates for raw and cooked products in the kitchen.
