Something you ate? Episode 3: Tales from the lab

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The Government of Canada and food industry maintain high standards for food safety practices. However, no system is perfect and outbreaks of enteric illness happen from time to time.

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Identifying outbreaks involves investigations conducted by epidemiologists and laboratories.

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Lab and surveillance experts identify outbreaks through various surveillance networks.

Matthew Gilmour, PhD, Director, Bacteriology and Enteric Diseases Program, Public Health Agency of Canada
PulseNet Canada is a national system that's used to quickly identify and respond to food-borne disease outbreaks. It's a virtual network that ties the public health labs of all provinces together by linking their computers and a central database of genetic fingerprints of bacteria. This is how outbreaks can be detected and tracked across the country.

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Lab experts also have access to the Canadian Network for Public Health Intelligence. This network is a system that helps with the sharing of information and the coordination of the public health response.

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Just as people are genetically different from each other, bacteria have genetic differences. The National Microbiology Laboratory uses leading-edge technology, called PFGE, to get a "genetic fingerprint" for bacteria specimens from the people who got sick.

Matthew Gilmour, PhD, Director, Bacteriology and Enteric Diseases Program, Public Health Agency of Canada
To fingerprint a bacterial pathogen, first we cut its DNA into several pieces. The segments of DNA are placed in a gel that's made of seaweed or algae, it's actually quite similar to really stiff gelatin.

Matthew Gilmour, PhD, Director, Bacteriology and Enteric Diseases Program, Public Health Agency of Canada
Then we run electricity through the gel, which causes the DNA fragments to separate based upon their lengths. So this arrangement of the DNA fragments by size actually looks like a bar code and represents the PFGE fingerprint.

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The Lab compares PFGE fingerprinting results to help figure out if cases of illness could be related to each other.

Matthew Gilmour, PhD, Director, Bacteriology and Enteric Diseases Program, Public Health Agency of Canada
If different samples have identical fingerprints then the infections MAY have been caused by the same food. If we then run the same test on bacterial pathogens that have been isolated from a suspect food sample, and we get the same fingerprint, we may very well have found the source of the outbreak.

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PFGE fingerprint testing is completed across the country at provincial and federal labs that are a part of the PulseNet Canada network.

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By sharing these results from human and food samples in real time into the PulseNet Canada database for analysis and comparison, outbreaks in any part of the country can be rapidly detected.

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To identify and respond to outbreaks, labs and epidemiologists across the country monitor the findings and identify trends that are shared on the PulseNet Canada online discussion board.

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For more information and updates, please visit our website at www.foodsafety.gc.ca

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A message from the Government of Canada.