Maybe we should just cook our salads

The spate of contaminated leafy greens sickening people in the US and Canada is continuing with the CDC announcing yet another outbreak. The CDC is currently recommending that US consumers should not eat any romaine lettuce and nor should retailers or restaurants serve or sell any until the source of this latest outbreak is established. (It is being conjectured that the source is likely in Monterey County, which produces 960 million heads of lettuce each year.)

So far there are 32 Americans and 18 Canadians infected with Shiga toxin-producing E. coli O157:H7. This outbreak is not the same strain as the latest one that was traced to contaminated canal water used for irrigation. Instead, it is the same strain as that of the 2017 outbreak where 25 illnesses were reported with nine hospitalised, two developing haemolytic uremic syndrome (HUS) and one fatality. The actual source of this outbreak was never unequivocally established.

HUS is a particularly nasty complication of Shiga toxin producing E. coli (STEC) infections. E. coli O157:H7 is the most common serotype but not the only bacteria that can cause HUS. In 2011, E. coli O104:H4-contaminated fenugreek seeds hit Germany with 800 of the 3800 people affected going on to develop HUS and 36 deaths. German doctors are concerned that the country will not have enough kidneys available for transplants in the future to cater for the needs of those who developed HUS following ingestion of the fenugreek seeds and sprouts.

Washing leafy greens will reduce the loads of pathogens but will not eliminate risk completely. As few as 10 E. coli bacteria can cause disease, and washing will never reduce the loads to a safe level. So what is really needed is a kill step. Boiled lettuce anyone?

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