Wednesday, March 26, 2014

So there's Listeria in your peanut butter...

I'm writing this in an attempt to quell the fears that have arisen in my fellow Minnesotans as they've read about, heard about, or been called about a recent food recall.  Parkers Farm of Coon Rapids, MN issued a voluntary recall of certain products due to the possibility of Listeria contamination on Friday 3-21-14.  Peanut butter, salsa, cheese, and spreads under a variety of brand names sold at a variety of stores nationwide are part of this particular recall. You can find the MN Department of Agriculture press release with a complete list of products and dates here.

I first heard about this on 3-22-14 because a friend shared our local CBS affiliate WCCO's Facebook post about the recall, with her personal lament that she eats a brand of salsa on the list.  Sad face.  I assured her that Listeria means her no harm (exceptions to this rule to follow).  Then, earlier this afternoon another friend posted on Facebook.  This time it was peanut butter...that she had eaten most of, much to her dismay.  I figured I ought to write something up.  And clearly my idea of starting a science blog that I was so excited about got lost in the shuffle of life after only one post.  Sheesh.

I would now like to take the opportunity to explain this type of recall.  Listeria is among several microorganisms that have been deemed as adulterants and are part of a zero-tolerance campaign for food safety.  This means that if at any time during an inspection process Listeria bacteria are found, that product and any product produced at the same facility over a certain period of time (of which I know not and am too lazy to find out) cannot be sold for human consumption.  What happened here is that many of these products had already made it to the marketplace and have been sold and likely consumed.  Or in the case of my peanut butter friend, definitely consumed.  The good news is that there haven't been any illnesses and certainly haven't been any outbreaks of illness associated with this recall.

Which brings us to the microbiology lesson portion of this blog!  Get out your pens and paper, there will be a quiz at the end.  Maybe, we'll see how I feel once we get there.  Listeria bacteria are found in soil, water, and some animals, including poultry and cattle, can be carriers.  So one can see how they may come to contaminate your food simply by proximity; pure happenstance.  Most often Listeria are associated with ready-to-eat products like hot dogs, deli meats and cheeses, and unpasteurized milk and milk products.  Listeria are killed by cooking and pasteurization, so how can they still contaminate your hot dog?  Aren't those gems pre-cooked?  Why yes, yes they are.  However, contamination can occur after cooking, but before packaging.  Okay, but refrigeration slows the growth of bacteria right?  True, true.  Well here's a fun fact about Listeria: it thrives at refrigerated temperatures.  Loves it!  Goes bananas!!  Seriously, I used to work in a clinical lab and when we cultured for Listeria we put the specimen in the fridge.  Okay, so it grows in the fridge.  But you've eaten countless sandwiches stacked high with turkey and ham slices and haven't gotten sick right?  Right.  There are several species of Listeria, but only one that causes human illness - Listeria monocytogenesL. monocytogenes can cause an illness called listeriosis.  The reason why you've been able to eat mass quantities of deli meats without coming down with listeriosis is because you're a healthy adult.  Listeriosis in the healthy person may cause a mild, acute febrile gastroenteritis (also known as tummy-ache with a fever; nothing the plop, plop, fizz, fizz of Alka-Seltzer can't alleviate).  Diarrhea is rare and most people that eat food contaminated with L. monocytogenes have no symptoms at all. 

Listeriosis is also quite rare.  Or rather, the manifestation of the illness that put Listeria on the zero-tolerance list is rare.  I was researching listeriosis for a grad school project a few years ago; at that time there were approximately 1600 cases annually.  In comparison to a more well-known foodborne pathogen like Salmonella, that's small potatoes; Salmonella is estimated to cause more than 1 million illnesses each year.  Listeria monocytogenes ranks a lowly 24th of 31 pathogens known to cause foodborne illness in total cases per year, but is 7th when it comes to hospitalizations and 3rd out of 31 in deaths.  Yikes!  So who's at risk?  The elderly, the immunocompromised (due to disease or certain medications), fetuses and newborn babies are at a much higher risk of invasive disease and death.  Invasive disease means that the bacteria get in your blood and/or your spinal fluid where it infects everything and causes your body to effectively shut down.  Invasive listeriosis is a whole other monster from what I described in the previous paragraphs.  Remember when I said there was an exception to the rule that Listeria meant no harm?  I shall now explain.  The following are some relatively recent listeriosis outbreaks:
  • 2010 - 14 illnesses, 7 hospitalizations, 2 deaths; associated with hog head cheese (a meat jelly made from swine heads....ugh.....)
  • 2007 - 5 illnesses, 5 hospitalizations, 3 deaths, 1 stillbirth; associated with consuming pasteurized milk
  • 2002 - multi-state outbreak; 54 illnesses, 8 deaths, 3 miscarriages/stillbirths; associated with sliced turkey deli meat
A pregnant woman with listeriosis may experience a mild, flu-like illness but then might lose the baby or her baby may be born very sick with invasive disease.  Listeriosis can be absolutely devastating.  

So what can you do?  If you are elderly (congrats on making it this far!) or very young (do you have your parent's permission to be online?), pregnant or immune-compromised:  avoid ready-to-eat meats, raw seafood (including smoked), and unpasteurized milk and milk products.  If you really want that deli sammy, you can steam the meat first as cooking does kill that little trouble making bacteria.  If you're a healthy person, Listeria really isn't anything to worry about.  You're far more likely to get sick from touching your computer keyboard.  Look it up.