Category Archives: E.coli O157

USA – Core Outbreak Table Update


Date Ref Pathogen Product(s) Total Investigation Status
11/24/2021 1044 Salmonella     Javiana Not Yet Identified 19 Active
11/17/2021 1043 E. coli O157:H7 Spinach See Outbreak Advisory Active
9/15/2021 1031 Salmonella Oranienburg Red, Yellow, and White Onions See Outbreak Advisory Active
9/15/2021 1025 Salmonella Thompson Seafood See Outbreak Advisory Active


Research – Evaluation of the use of ampicillin- and streptomycin-resistant Shiga toxin-producing Escherichia coli to reduce the burden of background microbiota during food safety studies

Wiley Online

Tracking artificially seeded foodborne pathogens in foods with high background microbiota is challenging. Wheat flour and its subsidiary products are known to carry a high native microbial load, which could interfere with tracking and enumeration of target organisms in such matrices. Shiga toxin-producing Escherichia coli (STEC) serogroups O26, O121, and O157:H7 were transformed with the pGFPuv plasmid encoding ampicillin resistance (+Amp) and green fluorescent protein and were additionally conferred resistance to streptomycin (+Amp + Strep) through exposure to incremental concentrations of the antibiotic. Growth characteristics of these antibiotic-resistant strains were compared to those of the nonresistant native strains (NR). The supplementation of ampicillin and ampicillin + streptomycin in growth media was evaluated for its ability to suppress growth of the native microbial load of three different commercial cake mixes. Antibiotic supplementation in growth media was successful in suppressing the native microbiota of the cake mixes, while the growth characteristics of the +Amp + Strep variants of the three STEC strains did not differ significantly from the NR strains (p > .05). These results indicate that STEC strains with ampicillin and streptomycin resistance markers have improved trackability over their wild-type counterparts when isolated from food matrices with high background microbiota. These strains would be advantageous for use in laboratory experiments on STEC survival in wheat and wheat derived products as their detection and enumeration can occur without interference from native microbial load.

USA – Outbreak Investigation of E. Coli O157:H7 – Spinach (November 2021)


Outbreak Investigation of E. Coli O157:H7 in Spinach (November 2021): Sample Image of Josie's Organics Baby Spinach

The FDA and CDC, in collaboration with state and local partners, are investigating illnesses in a multistate outbreak of E. coli O157:H7. According to the CDC, as of November 15, 2021, 10 people infected with the outbreak strain of E. coli O157:H7 have been reported from 7 states. Illnesses started on dates ranging from October 15 to October 27, 2021. Five people in this outbreak report eating spinach in the week before becoming sick and one person reported Josie’s Organics brand.

On November 15, 2021, the Minnesota Department of Agriculture reported that, as part of this outbreak investigation, a sample of Josie’s Organics Baby Spinach collected from the home of an ill person tested positive for E. coli O157:H7. This sample had a “Best If Used By” date of October 23, 2021 and is undergoing Whole Genome Sequencing (WGS) analysis to determine if the strain of E. coli O157:H7 present in the product sample matches the outbreak strain.

As WGS analysis of the sample is underway, FDA is tracing back the supply of the baby spinach in the positive product sample. Thus far, FDA has traced supply chains for this product back to a small number of farms in two different geographic regions and is deploying investigators along the supply chains of interest.

FDA and state partners are working with the firm to determine if additional products could be affected. This is an ongoing investigation and additional information will be provided as it becomes available.


Consumers, restaurants, and retailers, should not eat, sell, or serve Josie’s Organics Baby Spinach with a “Best If Used By” date of October 23, 2021. Josie’s Organics Baby Spinach is sold in a clear plastic clamshell with the Best If Used By Date on the top label.

Although this product is past expiration and should no longer be available for purchase, consumers should check their homes for product and discard it. If consumers froze fresh Josie’s Organics Baby Spinach, they should discard it.

Case Count Map Provided by CDC

Outbreak Investigation of E. Coli O157:H7 in Spinach: Case Count Map Provided by CDC (November 15, 2021)

Case Counts

Total Illnesses: 10
Hospitalizations: 2
Deaths: 0
Last Illness Onset: October 27, 2021
States with Cases: IA (1), IN (3), MI (1), MN (2), MO (1), OH (1), SD (1)

Research – Attachment of Shiga Toxin-Producing Escherichia coli (STEC) to Pre-Chill and Post-Chill Beef Brisket Tissue


Shiga toxin-producing Escherichia coli (STEC) has caused numerous foodborne illness outbreaks where beef was implicated as the contaminated food source. Understanding how STEC attach to beef surfaces may inform effective intervention applications at the abattoir. This simulated meat processing conditions to measure STEC attachment to adipose and lean beef tissue. Beef brisket samples were warmed to a surface temperature of 30 °C (warm carcass), while the remaining samples were maintained at 4 °C (cold carcass), prior to surface inoculation with an STEC cocktail (O26, O45, O103, O111, O121, O145, and O157:H7). Cocktails were grown in either tryptic soy broth (TSB) or M9 minimal nutrient medium. Loosely and firmly attached cells were measured at 0, 3, 5, and 20 min and 1, 3, 8, 12, 24 and 48 h. TSB-grown STEC cells became more firmly attached throughout storage and a difference in loosely versus firmly attached populations on lean and adipose tissues was observed. M9-grown STEC demonstrated a 0.2 log10 CFU/cm2 difference in attachment to lean versus adipose tissue and variability in populations was recorded throughout sampling. Future research should investigate whether a decrease in intervention efficacy correlates to an increase in firmly attached STEC cells on chilled carcasses and/or subprimals, which has been reported. View Full-Text

USA – E. coli outbreak linked to the Georgia National Fair in Perry Georgia

Food Poison Journal

The Associated Press reports tonight that Georgia state health officials are investigating whether E. coli (presumably, E. coli O157:H7) was spread at the Georgia National Fair held earlier this month.

The Georgia Department of Public Health said it has confirmed four cases of the illness among children who were at the event in Perry from Oct. 7 to Oct. 17, news outlets reported. Three of them are now hospitalized.

Hokanson said they’ve created an online survey that they hope will help them pinpoint the cause of the problem. Anyone who went to the fair can fill it out — even if they did not get sick after the event. State epidemiologists are working to determine what could have caused the outbreak by comparing activities between those who became sick and those who did not.

USA – Kentucky reports outbreak of E. coli due to food distribution

Food Poison Journal

Kentucky Cabinet for Health and Family Services reports that ten Kentuckians recently tested positive with a strain of E. coli O157:H7. Of the cases, two individuals developed a rare but serious condition called hemolytic uremic syndrome (HUS). Public health investigators have not yet identified the source of the outbreak but have noted that some sort of food distribution is likely.

The reported cases primarily include adults, many of whom reside in western Kentucky. No deaths linked to the outbreak have been reported but six people have been hospitalized. Health care providers have been notified of the outbreak and are advised to be alert for patients experiencing acute diarrheal illness, which could be associated with E. coli. This is a particular strain of E. coli that produces a type of toxin (Shiga toxin) that can be dangerous for those infected.

Research – Use of Acetic Acid to Partially Replace Lactic Acid for Decontamination against Escherichia coli O157:H7 in Fresh Produce and Mechanism of Action


Escherichia coli O157:H7 is frequently detected in ready-to-eat produce and causes serious food-borne diseases. The decontamination efficacy of lactic acid (LA) is clearly established. In this study, LA was mixed with acetic acid (AA) to reduce costs while achieving consistent or better inhibitory effects. Time-kill curves and inoculation experiments using fresh-cut spinach and arugula indicated that 0.8%LA+0.2%AA shows similar antibacterial effects to those of 1%LA. To determine whether 1%LA and 0.8%LA+0.2%AA exert antibacterial effects by similar mechanisms, proteomics analysis was used. The proteins related to macromolecule localization, cellular localization, and protein unfolding were uniquely altered after the treatment with 1%LA, and the proteins related to taxis, response to stress, catabolic process, and the regulation of molecular function were uniquely altered after the treatment with 0.8%LA+0.2%AA. Based on these findings, combined with the results of a network clustering analysis, we speculate that cell membrane damage is greater in response to LA than to 0.8%LA+0.2%AA. This prediction was supported by cell membrane permeability experiments (analyses of protein, nucleotide, ATP, and alkaline phosphatase leakage), which showed that LA causes greater membrane damage than 0.8%LA+0.2%AA. These results provide a theoretical basis for the application of an acid mixture to replace LA for produce decontamination. View Full-Text

USA – FDA Releases Report on Findings from Sampling of Romaine Lettuce in Yuma, AZ


Eurofins Food Testing UK

October 7, 2021

The FDA is releasing the findings of a sampling assignment for which FDA collected and tested romaine lettuce from commercial coolers in Yuma County, Arizona during February and March 2021. The agency tested the lettuce for Shiga toxin-producing Escherichia coli (STEC), specifically enterohemorrhagic Escherichia coli (EHEC), and Salmonella spp. This assignment was part of the FDA’s ongoing surveillance following multistate E. coli O157:H7 outbreaks of foodborne illness in recent years linked to or potentially linked to romaine lettuce.

The agency’s goal in conducting this assignment was to determine whether the target pathogens and specific strains may be present in romaine lettuce from the Yuma agricultural region, to help prevent foodborne illness when possible. If product that tested positive for EHEC or Salmonella was found, the Agency planned to work with industry and state regulatory partners to identify the cause (e.g., farm follow-up investigation) to inform future regulatory and/or research efforts and to develop strategies that could help preventive additional outbreaks.

The FDA collected 504 romaine samples for EHECs and Salmonella spp., with the testing performed by an independent laboratory on contract, as part of a pilot project. Each sample consisted of 10 subsamples, and each subsample was made up of at least 300 grams of romaine lettuce (whole heads, hearts or individual leaves).  Collecting and testing samples composed of multiple subsamples increases the probability of detecting pathogens if present, since microbial hazards may not be uniformly present.

During the assignment the FDA detected E. coli O130:H11 in one sample.  The isolate was found to be moderate to high risk and could be capable of causing severe illness in humans, though it was not linked to any known human illnesses, and no product ever reached consumers. The owner of the product did not harvest the remaining crop from the field where it was grown.

In response to the finding, FDA conducted an investigation at the farm to identify possible sources and routes of contamination. The FDA was able to collect romaine lettuce from the field, multiple samples of soil, water, sediment, and animal fecal material. FDA also assessed farm equipment and other surfaces. Only one of the total 24 samples yielded STEC (specifically, E. coli O116:H-). This sample came from the outer leaves of romaine lettuce. The strain was further characterized as low risk to human health, and FDA’s analysis indicated the strain was not linked with any past known foodborne illness outbreaks.

Helping to ensure the microbiological safety of leafy greens continues to be a priority of the FDA. Romaine lettuce and other leafy greens are among the most widely consumed vegetables in the United States and are an important part of a healthy diet. The agency is working on several fronts to help prevent microbial contamination of leafy greens and to prevent outbreaks of foodborne illness. Chief among these efforts is the FDA’s Leafy Greens STEC Action Plan (LGAP), which features public health approaches related to response, prevention and addressing knowledge gaps. The FDA continues to collaborate with industry, states, academia and other stakeholders through activities outlined in the LGAP to address this important public health issue.

USA – Jackson County Public Health Investigating Shiga toxin-producing Escherichia coli (STEC) cases

Jackson County

Jackson County Public Health is investigating an unusually high number of Shiga toxin-producing Escherichia coli (STEC) cases. Since August 8, 2021, 16 cases have been reported to Jackson County, and 12 (75%) of these cases have been hospitalized. Age range for cases is from 11 months to 65 years of age, with the median age being 23.5. Majority of the cases are in the teens and twenties. Of the total cases 62.5% are males.

Jackson County Public Health is working with the Oregon Health Authority on this outbreak investigation.  “Right now, we do not have a definitive hypothesis on what the source of infection may be. The genome sequencing, performed at the state public health lab, has not matched any other cases in the state or nationally,” states Dr. Jim Shames, Health Officer for Jackson County Public Health. “Therefore, we continue to do in-depth interviews with those that have tested positive to help us identify a possible source of exposure.”

Jackson County Public Health is asking medical providers to be aware of the increases in STEC cases in Jackson County and collect and test stool specimens on patients suspected to have bacterial gastroenteritis. Shiga-toxigenic Escherichia coli (including 0157, HUS, and other serogroups) are reportable infections to local and state public health.

Research – Nanoemulsified carvacrol as a novel washing treatment reduces Escherichia coli O157:H7 on spinach and lettuce

Journal of Food Protection

Fresh produce continues to be the main source of foodborne illness outbreaks in the United States implicating bacterial pathogens such as Escherichia coli O157:H7 (EHEC). The efficacy of nanoemulsified carvacrol (NCR) as a washing treatment in reducing EHEC on fresh produce was investigated. Fresh baby spinach, Romaine lettuce, and Iceberg lettuce leaves (2.5 cm diameter cores) were spot-inoculated with a five-strain cocktail of nalidixic acid resistant EHEC at ~ 6 log CFU/cm 2 . After air-drying for 1 h, 20 pieces of each inoculated produce leaves were immersed in water-based treatment solutions (200 ml/group), including water alone, 25 or 50 ppm free chlorine, and 0.25% or 0.75% NCR for 2 minutes. Inoculated produce leaves without any treatment served as baseline. Produce leaves were stored at 10°C and surviving EHEC populations were enumerated on days 0, 2, 7 and 14. The viability of EHEC following NCR treatments on the fresh produce was visualized under fluorescence microscope. NCR treatment at 0.75% immediately reduced EHEC populations on Iceberg lettuce by 1.3 log CFU/cm 2 as compared to the produce treated with water alone (P<0.05). Antimicrobial activity of NCR against EHEC was comparable to chlorine treatments on day 0 for all produce (P>0.05). After 14-days of storage at 10°C, populations of EHEC on 0.75% NCR treated Romaine lettuce were reduced by 2.3 log CFU/cm 2 as compared to the recovery from 50 ppm chlorine treated samples (P<0.05). Microscopic images revealed that EHEC cells were observed to be clustered on the baseline samples, indicating the development of cell aggregation, as compared to the scattered cells seen on NCR-treated leaf surfaces. Treatments with NCR did not significantly affect the color on the fresh produce leaves during the 14 days of storage at 10°C. Results of this study support the potential use of NCR as a water soluble natural antimicrobial wash treatment for controlling EHEC on fresh produce.