Journal Article

Outbreak of Shiga Toxin-Producing Escherichia coli (STEC) O157:H7 Associated with Romaine Lettuce Consumption, 2011

Schwensohn, Colin A., Khan, Faisal, Gladbach, Stephen, Slayton, Rachel B., Williams, Ian, Bennett, Sarah D., Yaffee, Anna Q., Turabelidze, George, Ayers, Tracy L., Gieraltowski, Laura B., Butler, Cindy, Davis, Marjorie L., Laufer, Alison S., Trees, Eija

2013

Overview

Shiga toxin-producing Escherichia coli (STEC) O157:H7 is the causal agent for more than 96,000 cases of diarrheal illness and 3,200 infection-attributable hospitalizations annually in the United States. We defined a confirmed case as a compatible illness in a person with the outbreak strain during 10/07/2011-11/30/2011. Investigation included hypothesis generation, a case-control study utilizing geographically-matched controls, and a case series investigation. Environmental inspections and tracebacks were conducted. We identified 58 cases in 10 states; 67% were hospitalized and 6.4% developed hemolytic uremic syndrome. Any romaine consumption was significantly associated with illness (matched Odds Ratio (mOR) = 10.0, 95% Confidence Interval (CI) = 2.1-97.0). Grocery Store Chain A salad bar was significantly associated with illness (mOR = 18.9, 95% CI = 4.5-176.8). Two separate traceback investigations for romaine lettuce converged on Farm A. Case series results indicate that cases (64.9%) were more likely than the FoodNet population (47%) to eat romaine lettuce (p-value = 0.013); 61.3% of cases reported consuming romaine lettuce from the Grocery Store Chain A salad bar. This multistate outbreak of STEC O157:H7 infections was associated with consumption of romaine lettuce. Traceback analysis determined that a single common lot of romaine lettuce harvested from Farm A was used to supply Grocery Store Chain A and a university campus linked to a case with the outbreak strain. An investigation at Farm A did not identify the source of contamination. Improved ability to trace produce from the growing fields to the point of consumption will allow more timely prevention and control measures to be implemented.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Adolescent / Adult / Aged / Aged, 80 and over / Agriculture / Analysis / Bacterial toxins / Bacterial Typing Techniques / Case-Control Studies / Causes of / Child / Child, Preschool / Colleges & universities / Confidence intervals / Consumption / Contamination / Diarrhea / Disease control / Disease Outbreaks / Disease prevention / E coli / Epidemics / Escherichia coli / Escherichia coli O157 - genetics / Escherichia coli O157 - isolation & purification / Farms / Female / Food contamination & poisoning / Food Microbiology / Genetic aspects / Health aspects / Hemolytic uremic syndrome / Hemolytic-Uremic Syndrome - epidemiology / Hemolytic-Uremic Syndrome - microbiology / Hemolytic-Uremic Syndrome - pathology / Humans / Hypotheses / Illnesses / Infant / Infections / Lactuca - microbiology / Lettuce / Male / Medical laboratories / Medicine / Metropolitan areas / Middle Aged / Odds Ratio / Outbreaks / Physiological aspects / Public health / Research Report / Shiga toxin / Shiga Toxin - isolation & purification / Studies / Toxins / United States - epidemiology / Vegetables / Veterinary Science