Two multistate outbreaks of a reoccurring Shiga toxin-producing Escherichia coli strain associated with romaine lettuce: USA, 2018–2019

Abstract

Leafy green vegetables are a common source of Shiga toxin-producing Escherichia coli O157:H7 (STEC O157) foodborne illness outbreaks. Ruminant animals, primarily cattle, are the major reservoir of STEC O157. Epidemiological, traceback, and field investigations were conducted to identify potential outbreak sources.Product and environmental samples were tested for STEC. A reoccurring strain of STEC O157 caused two multistate outbreaks linked to romaine lettuce in 2018 and 2019, resulting in 234 illnesses in 33 states. Over 80% of patients interviewed consumed romaine lettuce before illness. The romaine lettuce was sourced from two California growing regions: Santa Maria and Salinas Valley in 2018 and Salinas Valley in 2019. The outbreak strain was isolated from environmental samples collected at sites >90 miles apart across growing regions, as well as from romaine-containing products in 2019. Although the definitive route of romaine contamination was undetermined, use of a contaminated agricultural water reservoir in 2018 and contamination from cattle grazing on adjacent land in 2019 were suspected as possible factors. Preventing lettuce contamination from growth to consumption is imperative to preventing illness. These outbreaks highlight the need to further understand mechanisms of romaine contamination, including the role of environmental or animal reservoirs for STEC O157.

Interactions between Enterohemorrhagic Escherichia coli (EHEC) and Gut Commensals at the Interface of Human Colonoids

“…Variations in microbiota composition are a critical factor in determining host susceptibility to enteric infections ( 7 , 28 ). There is growing evidence that microbiota composition can also impact the course of EHEC-mediated disease, given that people infected with the same strain during an outbreak show a wide range of differential symptoms and disease progression ( 15 , 17 , 29 ). Here, we show that Bacteroides thetaiotaomicron and Enterococcus faecalis , two phylogenetically distinct commensal bacteria, increase EHEC virulence gene expression and attachment to epithelial cells ( Fig.…”

“…For instance, EHEC can take advantage of the resident gut commensals by using microbiota-derived molecules both as nutrients and as signals to regulate its virulence genes, including the LEE, since the T3SS expression is energetically costly and, therefore, tightly regulated ( 13 , 14 ). The observation that infected individuals with the same strain of EHEC manifest varying degrees of disease severity, suggests that variations in the microbiome could influence host susceptibility to EHEC infection ( 15 – 17 ). Furthermore, previous studies have shown that different members of the gut microbiota can affect EHEC virulence and disease ( 18 – 20 ).…”

Risk factors associated with the prevalence of Shiga-toxin-producing Escherichia coli in manured soils on certified organic farms in four regions of the USA

“…Adjacent land use for cowcalf rearing and the presence of feral pigs were implicated in the 2007 spinach outbreak due to E. coli O157:H7 in Central Coast California (Jay et al, 2007). More recently, the 2018 multi-state E. coli O157:H7 outbreak associated with romaine lettuce and potential contamination of water due to proximity to a large animal feeding operation highlights the need to investigate the proximity of livestock operations to fresh produce fields (Waltenburg et al, 2021). Berry et al (2015Berry et al ( , 2019 reported that 400 feet may not be adequate to limit the transmission of E. coli O157:H7 to produce crops close to a Concentrated Animal Feeding Operation (CAFO), and flies may have a role in leafy greens contamination (Berry et al, 2015(Berry et al, , 2019.…”

Broad time‐dependent transcriptional activity of metabolic genes of E. coli O104:H4 strain C227/11Φcu in a soil microenvironment at low temperature

“…During recent years, outbreaks caused by enterohemorrhagic Escherichia coli (EHEC), and hybrid enterohemorrhagic/enteroaggregative E. coli (EHEC/EAEC) were increasingly correlated with the consumption of non‐heated vegetables (Grant et al, 2008; Greig & Ravel, 2009; Hilborn et al, 1999; Marder et al, 2014; Waltenburg et al, 2022). In 2011, a novel hybrid EHEC/EAEC strain of serotype O104:H4 caused a large outbreak of disease in Germany and fenugreek sprouts were identified as the most probable source of infection (King et al, 2012; Robert Koch Institute, 2011).…”