By Donna Campisano, specialist, Communications, APHL

You’re on a road trip and stop at a fast-food restaurant for a quick meal—and wake up later that night with nausea, stomach cramps and diarrhea. You’re so sick, you go to the emergency room. As part of the workup, doctors there ask you where you ate and what you had. Suspecting you may be suffering from an intestinal foodborne illness caused by harmful bacteria such as Salmonella or E. coli, emergency room staff collect a stool sample.

But what happens to that sample? And how might it launch a foodborne illness investigation? We asked experts in the food safety field to walk us through the steps and highlight the critical role laboratories—particularly public health laboratories—have in solving the case.

Inside a foodborne illness investigation

How a foodborne illness case is investigated varies by state (different states/jurisdictions have different laws and procedures regarding disease reporting) and the capacity of the testing laboratories. A stool sample, for example, may be sent from the hospital to a commercial laboratory where scientists may do a rapid screening panel to determine what pathogen (Salmonella, E. coli or something else entirely) you’re suffering from.

That’s enough information for a health care provider to treat you, but it’s not enough information to determine if your case is linked to other sick people who ate the same type of food. Without that kind of extra-step detective work, outbreaks can’t accurately be detected and a public health response—say, inspecting a restaurant or issuing a food recall—can’t be confidently initiated.

This is where public health laboratories perform vital services.

 In the fast-food example presented above, your stool sample may be sent from the clinical laboratory to a public health laboratory for more comprehensive testing. After microorganisms from the sample are isolated, public health laboratory professionals use whole genome sequencing (WGS) to extract and analyze the pathogen’s DNA. WGS identifies every fragment of the DNA, thus helping scientists determine the pathogen’s exact genetic fingerprint and if it can be linked to other cases.

“WGS really drills down into what the pathogen is and tells us important things that impact the public’s health—like whether the pathogen has antimicrobial resistance or whether it is linked to another patient’s specimen,” said Alyssa Dickey, PhD, a food laboratory scientist with the New York State Department of Agriculture and Markets.

PulseNet: The “pillar” of the nation’s food safety system

When testing is complete, public health laboratory professionals upload the data to PulseNet, looking for those specimens that have a very closely matching DNA fingerprint.

PulseNet, dubbed the “pillar” of the US food safety system and coordinated by the US Centers for Disease Control and Prevention (CDC), is a national disease-surveillance network comprised of public health, food regulatory and agricultural laboratories. Using state-of-the-art technology like WGS, the PulseNet network identifies related clusters of food- or waterborne illnesses to detect disease outbreaks.

“The whole point of PulseNet,” said Kirsten Larson, APHL’s senior program manager, Food Safety, “is to take these seemingly disparate cases of illness and determine if the genetic fingerprint for each is similar enough that they’re likely linked. That’s how they determine if something might be going on, especially if there are several cases or a cluster of similar genetic fingerprints. These laboratory professionals work with their epidemiologists and environmental health counterparts to investigate these clusters that may eventually be recognized as outbreaks.”

Funding: Why it’s more important now than ever

Confirmed foodborne illnesses rose by 25% last year, highlighting the need for continued investment in the safety of the US food supply.

Last summer, for example, one of the worst Listeria outbreaks in 13 years occurred when 61 people in 19 states were sickened after eating certain types of Boar’s Head deli meats. Sixty of the 61 people were hospitalized; 10 people died.

WGS helped public health laboratory professionals in Maryland—where several of the sickened individuals lived—crack the case, identifying liverwurst as a source of the sickness and linking illnesses together. Thanks to their quick detective work, Boar’s Head announced it would stop manufacturing liverwurst and shutter indefinitely its Jarratt, VA, plant where the tainted products were produced.

This is just one more example of public health laboratories’ crucial role in food safety.

“The better resourced a public health laboratory is, the better able it is to protect the public’s health,” Larson commented. “WGS can help us put pieces of the puzzle together quickly so we can detect outbreaks and mount a timely public health response. It’s a very powerful tool,” she added, “but it’s costly. Public health laboratories need adequate funding to do the important work they do.”

The post What Happens When Food Makes You Sick? The Crucial Role of Public Health Laboratories appeared first on APHL Blog.

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