There’s been some hoopla in the food news this week. Six more E. coli serotypes (in addition to E. coli O157:H7) are now to be treated as adulterants by USDA when they are found in raw beef trim.
The addition of these toxin-producing E. coli serotypes to the pantheon of named adulterants is largely due to the efforts of Bill Marler. And I applaud his desire to advance food safety.
But what happens when an eighth serotype causes an illness outbreak? For example, E. coli O104:H4 the serotype that caused last summer’s massive outbreak in Germany, is not one of the “super six” newly named adulterants.
I was reminded of this problem yesterday while speaking with Dr. Raoult Ratard, State Epidemiologist with the Louisiana Department of Health and Hospitals. We were discussing the illness outbreak in several southern US states, and the shiga-toxin-producing E. coli O145 strain that was recovered from patients. As of today, there are 12 confirmed illnesses in Georgia (5), Louisiana (3, including a 21-month-old girl who did not survive), Alabama (2), Florida (1) and Tennessee (1).
I asked Dr. Ratard whether he could confirm that the Louisiana illnesses were due to E. coli O145. With a verbal shrug, he replied that he did not know; Louisiana does not do an immunological identification of E. coli strains, beyond determining whether or not they are E. coli O157:H7. He opined that this would be a waste of time and resources, given the number of different strains in circulation.
Instead, Louisiana looks for shiga-toxin producting E. coli, determines whether or not the strain is E. coli O157:H7, and runs a genetic profile (known as PFGE). The PFGE result is emailed to the CDC, and the culture is purified and shipped to the agency labs. As far as Louisiana is concerned, the exact identification of the E. coli serotype is interesting from an academic perspective, but not something that they care to spend time on.
After thinking about this for a couple of minutes, I found myself agreeing with Dr. Ratard. There was a time when determining the serotype was a useful tool in tracing the source of a disease outbreak. That tool has been supplanted by a much more precise and reliable tool, in the form of genetic profiling.
Which brings me back to USDA and the “super six serotypes” that are in the media spotlight. What the agency should have done – and what I proposed back in 2009 – was to simply declare ANY shiga-toxin producing E. coli as an adulterant.
- The toxin doesn’t care which serotype is producing it.
- The patients don’t care which serotype is making them ill.
- The epidemiologists no longer rely on serotyping to define an outbreak.
So why should USDA set up seven individual small targets (E. coli O157:H7 and the “super six”) instead of a single inclusive target known around the world as “shiga-toxin producing E. coli?
Beats me!
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