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Cracking the case: How Minnesotans helped unravel the peanut-salmonella outbreak

As Minnesota epidemiologists checked out a few salmonella cases around the state, they found four with something in common: peanut butter. But it was only later that nursing homes provided a eureka moment: All served the King Nut brand.

The Peanut Corp. of America plant in Blakely, Ga. -- the source of the salmonella outbreak -- has been shut down.
REUTERS/Matthew Bigg
The Peanut Corp. of America plant in Blakely, Ga. — the source of the salmonella outbreak — has been shut down.

There are a number of jobs where the work is randomly assigned — prince or pauper, the next customer who walks in the door is yours. That’s the way it happened for Minnesota Department of Health (MDH) epidemiologist Stephanie Meyer.

In the early part of last December, several cases of salmonella had been reported across the state, and Meyer was assigned to follow up on them. Two months later, she and her fellow MDH epidemiologist Carlota Medus were being recognized by the Centers for Disease Control and Prevention (CDC) and Sen. Amy Klobuchar, D-Minn., for helping unravel a multistate outbreak of peanut-butter related salmonella poisoning.

But Meyer and the MDH weren’t the first to detect that something was up.

“In this instance, really it started when California noticed that in San Diego County they had an increased number of cases [of this specific type of salmonella],” Meyer recalled. “And they posted it to PulseNet as ‘Hey, we’re seeing quite a few of these. We don’t usually see this. Is anyone else seeing it?'” PulseNet is a CDC program that keeps state health and agricultural departments abreast of developing infectious outbreaks.

Based on the California cases and those from other states, in late November the CDC issued a PulseNet report announcing a growing cluster of diarrheal illness caused by the bacteria Salmonella typhimurium.

When it comes to picking a host, salmonella prefers the darkened confines of the gastrointestinal tract of mammals, birds, and reptiles. A list of those most commonly infected includes chickens, turkeys, ducks, sheep, cows, pigs, and pets such as turtles, snakes, lizards and iguanas.

Sickened animals often asymptomatic
All of these animals can be sickened by salmonella infection, but they can often be asymptomatic — what’s termed a “carrier state,” where they go about their normal lives quietly shedding salmonella in their stool. So although salmonella prefers a live host, it can end up in the food we eat when foodstuffs are contaminated by animal waste. Occasionally an infected food worker can be the point source, too.

In 2007 there were a number of small salmonella outbreaks here in Minnesota. They came from the likes of chickens (the live variety), a puffed-rice-and-corn snack, pet turtles, dry pet food, frozen pot pies, tomatoes at a sandwich shop, and peanut butter. By mid-December peanut butter was at the top of Medus and Meyer’s list.

“Even our four first cases, they had all eaten peanut butter. And nothing else, not even the common stuff you’d expect to see in Minnesota, like ‘Yes, we all ate Gold’n Plump chicken,’ because everyone eats Gold’n Plump chicken, and you see a lot of it. Bananas or apples are common produce items that you see people eating — they didn’t even have those in common. But they all ate peanut butter.”

Carlota Medus
Carlota Medus

As more sporadic cases trickled in — most from northern Minnesota, a few from the metro area — the peanut-butter lead didn’t seem to be going anywhere: It couldn’t be associated with one specific brand, or one specific source. Then came a new cluster of cases from two long-term care facilities (aka nursing homes) and an elementary school, all three in northern Minnesota.

Critical break: an isolated group
For an epidemiologist tracking a food-borne epidemic, this was a critical break. Now Meyer and Medus had an isolated group of people with a common food source. “Same menu, same things,” Meyer told me. “The only downside is that it’s harder to specifically ask people, ‘Do you remember did you eat this specific food item?’ But considering that we had more than one institution, that really helped.”

Asking people to recall what they’ve eaten in the last week is a lot of what Meyer does. This kind of detective work doesn’t involve poking around walk-in coolers at restaurants and cafeterias with a magnifying glass and a Petri dish. It involves contacting the infected individual on the phone and getting detailed diet information. In this case, Meyer and Medus worked with the Minnesota Department of Agriculture to get invoices from the food distributors used by each of the facilities over the preceding couple of weeks. And then the tedious work of cross-referencing began.

Their eureka moment came on Jan. 5. “That’s when we found out all three of those institutions had received King Nut peanut butter. And that was the only thing that they had in common.” Adding to the weight of evidence was a cluster of cases from an institution in Oregon that was using the same food distribution company. “It was from a different Sysco distributor, but since it was Sysco and ours was Sysco, we just said, ‘Hey, can we look at your invoices, too?’ And that institution had also received King Nut peanut butter,” Meyer recalled.

‘What’s the deal with the King Nut brand?’
“Shortly after that, we asked both our department of agriculture and the FDA if they could do any sort of informal looking,” Meyer recounted. ” ‘What’s the deal with the King Nut brand? Where is it made? Do they happen to manufacture their peanut butter in the same plant as any other big peanut butter people? Could these name-brand jarred peanut butters be made in the same plant as this institutional peanut butter? Is it all the same peanut butter under different brands?’ “

I asked Meyer about the balance of responsibility one has at that moment. When do you blow the horn? When do you know enough to be certain, to ask people to stop eating a certain product?

“As much as people don’t want to talk about the balance in dealing with money-type issues — and we try to keep ourselves separate from all that — you do have to think that if you’re wrong, you’re costing people millions of dollars and you could be costing people’s jobs. The after-effects could be horrendous. But if you’re right and yet do nothing, those after-effects could be horrible, too.”

Adding to their suspicion was the fact that they were still seeing a swath of new cases across northern Minnesota, and “All of them were ordering from this Sysco in North Dakota,” Meyer told me. “And then it’s ‘What does Sysco North Dakota distribute that Sysco Minnesota does not?’ And the one big thing was King Nut peanut butter.”

Confidence shaken by CDC data
The confidence in their diagnosis was shaken a bit by national data that the CDC was compiling.  “The statistics weren’t really coming out for us in the national study. No one else was seeing sporadic cases that all said ‘yes’ to eating peanut butter or some kind of peanut-butter product. It just wasn’t coming together.”

Meyer and Medus formulated a plan. “At the very least, let’s try and get a jar of this peanut butter to test, and if we get anything off this, we know we’re barking up the right tree.” A regional representative from the Minnesota Department of Agriculture secured a 5-pound container of King Nut peanut butter from one of the institutions and drove it back to the MDA lab in the Twin Cities for testing. By Jan. 9, the cultures were coming back positive for salmonella.

“To me, it was a done deal,” Meyer said. “We told them [the CDC] that’s what we had, and we said, ‘We don’t have proof that this can explain everybody. We can’t explain even all of our cases with this brand of peanut butter, but something is wrong, and you shouldn’t find salmonella in peanut butter.” The 5-pound container had been partially used, raising the possibility that a sick food worker could have contaminated it. But cultures from the deepest, undisturbed portion of the tub were also positive. 

“Over the weekend we did the check that you do on your own: ‘Would you feel comfortable with your grandparents in a long-term care facility eating this peanut butter over the weekend? Is that OK?’ And we kind of all agreed, ‘No, it is not OK. Something is wrong with this peanut butter. Even if it turns out not to be the type of salmonella that is part of this outbreak.’ “

“So the main message we decided to put out right away was, ‘We found salmonella in this type of peanut butter. If you’re an institution that serves this type of peanut butter, don’t serve it. And we’re working on it.’ “

Production stopped, investigation speeds up
On Jan. 9, the day the MDA cultures returned positive, officials from the FDA and the Georgia Department of Agriculture began inspecting the Peanut Corp. of America (PCA) plant, where King Nut peanut butter is produced exclusively. PCA stopped production that day, and began product recalls the following day. Thereafter, the investigation hit hyper-drive. Cultures from other state health departments began showing the same salmonella, with the exact same genetic fingerprint.

Meyer, Medus, the MDH and MDA were right, but they still had one question: Why was it that some of the early cases seemed to be linked to national brand, jarred peanut butters (which they now knew for sure had no connection to the Georgia plant)? The answer surprised them.

“Eating jarred peanut butter was just a proxy for the fact that they liked peanut butter and that they liked peanut butter snacks,” Meyer recalled. “When it comes to ‘Do you remember if you ate these particular snacks in the week before your illness?’ people just aren’t really good about it.” You can get a sense for how ubiquitous peanut-butter paste is in snacks by looking at the number of them affected by the recall; people with peanut allergies already knew this.

Meyer and her colleagues led the way in solving this latest outbreak. A CDC news release on the history of the investigation highlights the work of the MDH, which was also instrumental in solving the national tainted-salsa outbreak last year. (MDH was able to perform an ingredient-specific analysis of what patrons ate at a particular restaurant, pinning the outbreak on tainted jalapenos.)

Meyer acknowledges MDH’s successes but spreads the credit widely.

Quick follow-up important
“Most of the time, it’s because we follow up quickly with our patients. I think that the clinicians in Minnesota are probably better than anywhere about reporting diseases to us in a really timely manner,” she explained. “I don’t think there is any state that does it better than our people. Infection-control practitioners know they have to report. Doctors and nurses know they have to report, and they do it quickly,” she continued.

And according to Meyer, speed is the key. “As soon as we get those reports, we follow up with those people right away. So instead of it being a month-and-a-half later that we’re calling them and asking what they ate six weeks ago, we’re calling them a week-and-a-half or two weeks after their illness and saying, ‘I know it is hard to remember, but let’s talk about what you ate.'”

A perplexing, complicated case fell into Meyer and Medus’ lap, and they solved the puzzle faster than anyone else. Their work may well have saved a lot of people from real suffering, or worse. Not a bad month or two’s work.

“Sometimes, by the luck of the draw, you get an exciting one and you figure it out and then you feel really good,” Meyer admitted.

You can find updates from the CDC on the peanut-butter salmonella situation here. And here‘s an interesting Klezmer-backed video of live salmonella.
Dr. Craig Bowron is a Twin Cities internist and writer who reports on medical topics for MinnPost. He can be reached at cbowron [at] minnpost [dot] com.