Tons of Romaine Lettuce Has Been Removed

Creative Diagnostics - Food & Feed Analysis

Tons of Romaine Lettuce Has Been Removed

November 22, 2018

Because there is an outbreak of Escherichia coli O157:H7 illnesses in multiple states, which seems to be associated with romaine lettuce. In the past 24 hours, it can be said that tons of romaine lettuce have been removed from the store shelves in the United States. The U.S. Food and Drug Administration (FDA), Centers for Disease Control and Prevention (CDC) and local agencies are working on investigating it. At the same time, the Public Health Agency of Canada (PHAC) and Canadian Food Inspection Agency also join in together to investigate with U.S. agencies due to a similar outbreak in Canada.

Back to Tuesday, there has been a report that 32 people was infected in the United States and 18 in Canada. In the United States, those who infected with the strain of Shiga toxin-producing Escherichia coli O157:H7 live in 11 different states. The first illnesses began on Oct.8 to Oct. 31. As we can see, for this outbreak, the average interval between when a person becomes sick and when the sickness is reported to CDC is 20 days. There are 13 out of 32 people had been send to hospital. While one of them developed hemolytic uremic syndrome, which may lead to kidney failure. The 18 ill people in Canada live in two provinces, that is Ontario and Quebec. It has been confirmed that they are infected with the same DNA fingerprint of E. coli O157:H7 bacteria as the U.S. patients. Fortunately, no death has been reported so far on either side of these two countries.

Up to now, epidemiologic evidence from the United States and Canada indicates that romaine lettuce is a likely source of the outbreak. Although we don’t know where these contaminated lettuces were grown, the FDA is working on a traceback investigation to determine the source of the contaminated lettuce. In addition, laboratory analysis of these lettuce samples which may have a relationship to the current outbreak is been done by both FDA and states.

On Nov. 20, CDC advised public that consumers should not eat any romaine lettuce until more is known about the source of the contaminated lettuce and the status of the outbreak.


Escherichia coli

Figure 1. SEM micrographs of E. coli, before (a and b) and after (c and d) one-week starvation.

E. coli bacteria (Figure 1) usually live in the intestines of human and animals and consists of a diverse type of bacteria. Although most E. coli are harmless and contribute to human intestinal tract healthy, some of them are pathogenic. That E. coli will cause sickness such as diarrhea and some other illness outside of the intestinal tract. Therefore, pathogenic E. coli strains are grouped to pathotypes and those linked to diarrhea are called as diarrheagenic E. coli. They can be transmitted through contaminated water or food and even through contact with animals or people.

E. coli O157:H7 is a kind of E. coli that can cause disease by secreting a toxin named Shiga toxin, usually using STEC for short.

The DNA of the E. coli bacteria in the current outbreak has the same DNA fingerprint as the E. coli strain isolated from sick people in a 2017 outbreak. In 2017, that outbreak was associated with leafy greens in the USA and with romaine lettuce in Canada. However, the outbreak strain from this past spring’s outbreak does not match current patients.


Kim, T. , & Han, J. I. . (2013) 'Fast detection and quantification of Escherichia Coli using the base principle of the microbial fuel cell', Journal of Environmental Management, 130(Complete), 267-275.

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