Mike the Mad Biologist

STEC Surveillance: UR DOING IT WRONG?

There’s some good news and bad news regarding E. coli surveillance in meat products. The good news:

The pathogenic Shiga toxin-producing Escherichia Coli (pSTEC) serotypes known collectively as the “Big Six” will soon be banned from U.S. meat, a top expert told a meat industry conference Thursday.

Action to declare the six non-O157:H7 serotypes as adulterants in meat could come as early as next week, according to Mohammad Koohmaraie, chief executive officer for the meat division of IEH Laboratories & Consulting Group based in Lake Forest Park, WA.

For certain, he says, the Big Six — O26, O111, O103, O121, O45 and O145 — will be listed as adulterants no later than one year from now.

The only STEC currently listed as an adulterant is E. coil O157:H7, which has been the most virulent strain in the U.S. for the past two decades. It was listed as adulterant in 1994 by the Clinton Administration following the Jack in the Box outbreak.

Did you catch what’s missing? Let’s see. We got O26, O111, O103…wait a minute, what about O104:H4? You know, the E. coli serotype responsible for the single most deadly food outbreak EVAH! Didn’t seem to make the cut. Maybe this is like the Oscars or something.

Seriously, we don’t want to include every serotype–that would be untenable. But that’s the whole problem: we’re using a technology that nearly a century old.

If we want to detect STEC–shiga toxinogenic (producing) E. coli–then we shouldn’t be focusing on serotypes. Yes, if you grow up a lab culture, there are simple rapid serotype-based diagnostics that can be used. But once we’re in the lab anyway, why not use PCR? It’s been nearly thirty years since PCR was developed, and it’s routinely used in forensics. If you’re growing a lab culture, to do a quick DNA prep and look for the genes that encode shiga toxin isn’t that much more work. I’m not asking for whole genome sequencing, even though it’s been used for monitoring hospital outbreaks. That is expensive and not fast. But PCR can be done in an afternoon. And I’m sure some entrepreneurial type could figure out how to make a really fast and quick kit.

Every year, the Microbiological Data Program (soon to be phased out thanks to agricultural lobbyists) usually discovers a new shiga-toxin producing strain, so serotyping really isn’t sufficient.

To return to the snarky section, under the new rules, O104:H4 still wouldn’t be classified as an adulterant because it wouldn’t be one of the listed serotypes. If you’re worried about shiga toxin, then focus on detecting shiga-toxin producers.

It’s time for food, and specifically STEC, surveillance, to enter the last two decades of the twentieth century.

Comments

  1. #1 Ketil Tveiten
    August 22, 2011

    Hold on… so up until now, E.coli has been a legal food additive in the US?

  2. #2 hibob
    August 23, 2011

    If I had to hazard a guess, I’d say PCR tests aren’t approved because they would find pSTEC positive samples so often that the meat industry might be inconvenienced.

    Medium-well for me, thanks.

  3. #3 Civersen
    August 24, 2011

    I agree if we are looking for STEC we should look for the stx genes using PCR. However it is not so simple as the stx genes are comprised of subtypes, not all of which are pathogenic to humans. There needs to be a combination of PCR targets to identify pathogenic STEC but these should be based on virulence genes (such as agg and eae) not serotype genes.

  4. #4 Margaret
    August 26, 2011

    It’s distressing to say the least to know that the MDP is destined to be phased out, just exactly when we should be funding it more, with 7 known STEC adulterants out there.
    We have the science and we have brilliant scientists, but we don’t have a public or a Government willing to understand or listen to the science….. Oh wait, we’re “the greatest country in the world” and “we have the safest food supply in the world” !

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