Category Archives: E.coli 045

Research – Investigation of On-Farm Transmission Routes for Contamination of Dairy Cows with Top 7 Escherichia coli O-Serogroups


Shiga toxin-producing Escherichia coli (STEC) are foodborne bacterial pathogens, with cattle a significant reservoir for human infection. This study evaluated environmental reservoirs, intermediate hosts and key pathways that could drive the presence of Top 7 STEC (O157:H7, O26, O45, O103, O111, O121 and O145) on pasture-based dairy herds, using molecular and culture-based methods. A total of 235 composite environmental samples (including soil, bedding, pasture, stock drinking water, bird droppings and flies and faecal samples of dairy animals) were collected from two dairy farms, with four sampling events on each farm. Molecular detection revealed O26, O45, O103 and O121 as the most common O-serogroups, with the greatest occurrence in dairy animal faeces (> 91%), environments freshly contaminated with faeces (> 73%) and birds and flies (> 71%). STEC (79 isolates) were a minor population within the target O-serogroups in all sample types but were widespread in the farm environment in the summer samplings. Phylogenetic analysis of whole genome sequence data targeting single nucleotide polymorphisms revealed the presence of several clonal strains on a farm; a single STEC clonal strain could be found in several sample types concurrently, indicating the existence of more than one possible route for transmission to dairy animals and a high rate of transmission of STEC between dairy animals and wildlife. Overall, the findings improved the understanding of the ecology of the Top 7 STEC in open farm environments, which is required to develop on-farm intervention strategies controlling these zoonoses.

USA -USDA Will Expand non-O157 STEC Testing to Ground Beef

Food Poisoning Bulletin

According to an announcement in the Federal Register, the USDA will expand non-O157 STEC (Shiga toxin-producing E. coli) testing to ground beef, bench trim, and other raw ground beef components. The non-O157 strains include what’s called the “Big Six” E. coli strains: E. coli O26, O45, O103, O111, O121, and O145.

Research – Shiga toxin-producing Escherichia coli (STEC) and food: attribution, characterization, and monitoring


Strains of pathogenic Escherichia coli that are characterized by their ability to
produce Shiga toxins are referred to as Shiga toxin-producing E. coli (STEC). STEC
are an important cause of foodborne disease and infections have been associated with a wide range of human clinical illnesses ranging from mild non-bloody
diarrhoea to bloody diarrhoea (BD) and haemolytic uraemic syndrome (HUS)
which often includes kidney failure. A high proportion of patients are hospitalized,
some develop end-stage renal disease (ESRD) and some die.
The Codex Committee on Food Hygiene (CCFH) has discussed the issue of STEC
in foods since its 45th Session, and at the 47th Session, in November 2015, it was
agreed that it was an important issue to be addressed (REP 16/FH, 2015)2
. To
commence this work, the CCFH requested the Food and Agriculture Organization
(FAO) and the World Health Organization (WHO) to develop a report compiling
and synthesizing available relevant information, using existing reviews where
possible, on STEC. The CCFH noted that further work on STEC in food, including
the commodities to be focused on, would be determined based on the outputs of
the FAO/WHO consultation.
The information requested by CCFH is divided into three main areas: the global
burden of disease and source attribution; hazard identification and characterization; and monitoring, including the status of the currently available analytical
methods. This report provides an overview of the work undertaken in response to
the request from the CCFH and provides the conclusions and advice of the Expert
Group based on the currently available information.

Research – Survey of Intact and Nonintact Raw Pork Collected at Retail Stores in the Mid-Atlantic Region of the United States for the Seven Regulated Serogroups of Shiga Toxin–Producing Escherichia coli

Journal of Food Protection


A total of 514 raw pork samples (395 ground or nonintact and 119 intact samples) were purchased at retail stores in Pennsylvania, Delaware, and New Jersey between July and December 2017. All raw pork samples were screened for serogroup O26, O45, O103, O111, O121, O145, or O157:H7 cells of Shiga toxin–producing Escherichia coli (STEC-7) using standard microbiological and molecular methods. In short, 21 (5.3%) of the 395 ground or nonintact pork samples and 3 (3.4%) of the 119 intact pork samples tested positive via the BAX system real-time PCR assay for the stx and eae virulence genes and for the somatic O antigens for at least one of the STEC-7 serogroups. However, none of these 24 presumptive-positive pork samples subsequently yielded a viable isolate of STEC displaying a STEC-7 serogroup-specific surface antigen in combination with the stx and eae genes. These data suggest that cells of STEC serogroups O26, O45, O103, O111, O121, O145, or O157:H7 are not common in retail raw pork samples in the mid-Atlantic region of the United States.

  • None of the 514 retail raw pork samples were positive for STEC-7.

  • Four of 514 raw pork samples harbored E. coli of unknown serogroup containing stx and eae.

  • STEC-7 are uncommon in retail raw pork samples in the U.S. mid-Atlantic region.


Research – Response to Questions Posed by the Food and Drug Administration Regarding Virulence Factors and Attributes that Define Foodborne Shiga Toxin–Producing Escherichia coli (STEC) as Severe Human Pathogens

Journal of Food Protection


The National Advisory Committee on Microbiological Criteria for Foods (NACMCF or Committee) was asked to report on (i) what is currently known about virulence and pathogenicity of Shiga toxin–producing Escherichia coli (STEC) and how they cause illness in humans; (ii) what methods are available to detect STEC and their specific virulence factors; and most importantly (iii) how to rapidly identify foodborne STEC that are most likely to cause serious human disease. Individual working groups were developed to address the charge questions, as well as to identify gaps and give recommendations for additional data or research needs. A complete list of Committee recommendations is in Chapter 4.

STEC infections cause illnesses that range in severity from diarrhea to diarrhea with grossly bloody stools, called hemorrhagic colitis (HC), to the life-threatening sequela of infection, the hemolytic uremic syndrome (HUS). STEC are ingested in contaminated food or water or through direct contact with infected animals or people. Of all STEC that cause disease in the United States, E. coli O157:H7 (O157) causes the most outbreaks and the largest number of cases of serious illness (as assessed by the number of patients hospitalized or with HUS). The infectious dose 50% (ID50) of O157 is low (estimated to be 10 to 100 bacteria). As determined in animal models, these bacteria bind to enterocytes in the large intestine through the intimin outer membrane protein (the gene for intimin is eae), attach and efface the mucosa, and elaborate Shiga toxin (Stx) that passes from the intestine through the bloodstream to sites in the kidney. Certain Stx subtypes are more commonly associated with severe STEC human illness, e.g., Stx2a, Stx2c, and Stx2d. The serogroups (O antigen type only) linked to most cases of illness in the United States are O157, O26, O103, O111, O121, O45, and O145 in order of decreasing incidence. STEC disease is linked most often to foods of bovine origin and fresh produce; disease burden attributed to beef and dairy products is broadly similar in numbers to that attributed to fresh produce.

Stx production, a phage-encoded trait, and intimin, but not the O antigen type, are major drivers of pathogenicity. Thus, predictions of the pathogenic potential of STEC can be made based on Stx subtype and the potential of the bacteria to attach in the intestine. The combination of virulence genes in E. coli that has led to the most severe disease is stx2a with aggR (a genetic marker for enteroaggregative E. coli [EAEC]). The second-highest risk group are those O157 STEC that have stx2a and eae, followed by that same combination in O26, O103, O111, O121, O45, or O145. The combinations of stx1a and stx2a, or stx2a and stx2c, or stx2d with eaeare also of particular concern. The lack of eae suggests a reduced potential for human disease except when aggR or stx2d is present. There have been a few exceptions to this hierarchy, such as O103 that produce only Stx1 and O113 that is eae negative.

The protocols currently used by the U.S. Food and Drug Administration (FDA), U.S. Department of Agriculture–Food Safety and Inspection Service (USDA-FSIS), clinical laboratories and public health laboratories (PHLs), and the food industry include enrichment, culture, multiplex real-time PCR (RT-PCR), toxin immunoassays, biochemical characterization, DNA-based serotyping, DNA microarray, and whole genome sequencing (WGS). The advantages and limitations of each method are summarized in this report. New and developing high-throughput methods are discussed and include metagenomics, digital PCR, biosensors, and microarray.

STEC disease prevention has been and will continue to be driven by improvement in outbreak detection, investigation, and food industry practices. Highlights of Committee recommendations include the following:

  • Develop a new universal enrichment culture medium that can be broadly used for all STEC in any food.

  • Explore high-throughput methods that can detect STEC virulence factor genes directly from enrichment medium and develop and/or improve methods that can ascertain that all critical STEC markers found in the enrichment broth are within the same cell to eliminate the need to isolate the organism.

  • Expand systematic sampling of food, animals, and water for STEC.

  • Explore ways for industry to share test data anonymously.

  • Fund academic research on (i) the regulation of toxin expression and the phages that encode toxin; (ii) mechanisms of attachment by eae-negative STEC; (iii) oral-infection animal models or cell culture models that are more reflective of human disease; and (iv) human host factors that influence the outcome of STEC infection.

  • Link standardized epidemiological, clinical, and STEC WGS data to monitor trends in recognized and emerging virulence attributes such as Stx type and phage profiles.

  • Further develop WGS methods to (i) predict toxin levels produced by an STEC and (ii) generate a classification scheme based on genomic clusters.

The Committee agrees that a combination of genetic characteristics (attributes) exist that signal potentially high-risk STEC and that these STEC will eventually be identifiable using high-throughput techniques that analyze gene profiles. Thus, to rapidly identify foodborne STEC that are most likely to cause serious human disease, the Committee recommends that STEC analyses move toward using virulence markers rather than serogroup or serotype to identify pathogens. The Committee concurs that as ease of use increases and costs decrease, culture-independent diagnostic tests (CIDTs) based on genomic clusters or lineages will be more broadly used to predict whether an STEC isolate is likely to cause serious human disease.

Executive summary of the charge.

STEC are a large, diverse group of bacteria that are characterized by the production of Stx. There are two main Stx types, designated Stx1 and Stx2, and within each are many subtypes. Currently, there are three known Stx1 (Stx1a, Stx1c, and Stx1d) and seven known Stx2 (Stx2a, Stx2b, Stx2c, Stx2d, Stx2e, Stx2f, and Stx2g) subtypes, but some of these are produced mostly by environmental- or animal-associated strains. Thus far, Stx1a, Stx2a, Stx2c, and Stx2d are the subtypes most frequently implicated in human illness. There are estimated to be >400 known STEC serotypes that can produce any of the Stx types, subtypes, or combination of subtypes. However, only a subset of these STEC serotypes have been associated with human illness. Furthermore, the production of Stx alone without other virulence factors, such as intimin, has been deemed to be insufficient to cause severe human illness.

Research -Microbiological Testing Program for E. coli O157:H7 and non-O157 Shiga Toxin-Producing E. coli: Individual Positive Results for Raw Ground Beef (RGB) and RGB Components


Table 1. Raw Ground Beef Products (RGB) Analyzed for E. coli O157:H7, Current Calendar Year

Sample Source1 Collection Date Where Collected Product Status Positives this Year Samples Analyzed this Year Total Positives2 Total Samples Analyzed2
Federal RGB Verification, Beef Oct 15, 2018 MN Held 4 9,541 540 238,301
Federal RGB Verification, Beef Oct 9, 2018 NC Held 3 9,297 539 238,057
Federal RGB Verification, Beef Mar 26, 2018 OR Held 2 3,085 538 231,845
Federal RGB Verification, Beef Feb 8, 2018 CA Held 1 1,704 537 230,464


Web Content Viewer (JSR 286)



Microbiological Testing Program for E. coli O157:H7 and non-O157 Shiga Toxin-Producing E. coli: Individual Positive Results for Raw Ground Beef (RGB) and RGB Components

View by Year:  
2018 Positive Results
2017 Positive Results
2016 Positive Results
2015 Positive Results
2014 Positive Results
2013 Positive Results
2012 Positive Results
2011 Positive Results
2010 Positive Results
2009 Positive Results
2008 Positive Results
2007 Positive Results
2006 Positive Results
2005 Positive Results
2004 Positive Results
2003 Positive Results
2002 Positive Results
2001 Positive Results

The table below includes all positive results as of November 4, 2018.

Table 1. Raw Ground Beef Products (RGB) Analyzed for E. coli O157:H7, Current Calendar Year 

Sample Source1 Collection Date Where Collected Product Status Positives this Year Samples Analyzed this Year Total Positives2 Total Samples Analyzed2
Federal RGB Verification, Beef Oct 15, 2018 MN Held 4 9,541 540 238,301
Federal RGB Verification, Beef Oct 9, 2018 NC Held 3 9,297 539 238,057
Federal RGB Verification, Beef Mar 26, 2018 OR Held 2 3,085 538 231,845
Federal RGB Verification, Beef Feb 8, 2018 CA Held 1 1,704 537 230,464

1Sample Sources may include these types of establishments and samples:

  • Federal (verification; follow-up)
  • Retail (verification; follow-up)
  • State (verification; follow-up)
  • Import (verification; follow-up). For Import samples, the column “Where Collected” is defined as Country of Origin. <!–
  • Source may also refer to the type of product (beef, veal, or mixed), as listed on the product label.
  • –>

2Totals: “Total Positives” and “Total Samples Analyzed” are the totals since FSIS began its testing program to detect E. coli O157:H7 in raw ground beef on October 17, 1994.

The table below includes all positive results as of November 4, 2018.

Table 2. Raw Ground Beef Components (RGBC) Analyzed for Target STECs, Current Calendar Year3

Sample Source4 Collection Date Target STECs Where Collected Product Status Posi-
tives this Year
Samples Analyzed this Year5 Total Posi-
Total Samples Analyzed6
Trim Verification, Beef Oct 18, 2018 O111 PA Held 19 6,594 415 59,239
Trim Verification, Beef Oct 9, 2018 O157:H7 SD Held 18 6,262 414 58,907
Trim Verification, Beef Sep 5, 2018 O157:H7 PA Held 17 5,641 413 58,286
Trim Verification, Beef Aug 14, 2018 O103 PA Held 16 5,018 412 57,663
Trim Verification, Beef Jun 6, 2018 O157:H7 MO Held 15 3,583 411 56,228
Trim Verification, Veal Jun 6, 2018 O26 PA Held 14 3,428 410 56,073
Follow-up to RGBC Positive, Beef May 30, 2018 O103 PA Held 13 3,266 409 55,911
Follow-up to RGBC Positive, Beef May 29, 2018 O103 PA Held 12 3,266 408 55,911
Trim Verification, Beef May 21, 2018 O157:H7 TX Held 11 3,147 407 55,792
Trim Verification, Beef May 16, 2018 O103 PA Held 10 2,968 406 55,613
Trim Verification, Beef May 15, 2018 O103 NY Held 9 2,968 405 55,613
Trim Verification, Beef May 9, 2018 O103 PA Held 8 2,968 404 55,613
Other RGBC Verification May 9, 2018 O157:H7 NE Held 7 2,968 403 55,613
Trim Verification, Beef Mar  19, 2018 O157:H7 NM Held 6 1,814 402 54,455
Trim Verification, Beef Mar 1, 2018 O121 ID Held 5 1,507 401 54,148
Trim Verification, Veal Feb 27, 2018 O103 WA Held 4 1,347 400 53,988
Follow-up to RGBC Positive, Beef Jan 27, 2018 O45 WI Held 3 583 400 53,225
Other RGBC Verification Jan 4, 2018 O157:H7 SD Held 2 107 399 52,749
Trim Verification, Beef Dec 28, 2017 O157:H7 WI Held 1 107 398 52,749

Research – USA – Microbiological Testing Program for Escherichia coli O157:H7 and non-O157 Shiga toxin-producing Escherichia coli (STEC)


FSIS considers raw, non-intact beef products or the components of these products found to have six Shiga toxin-producing Escherichia coli (STEC) to be adulterated, in addition to E. coli O157:H7. (Refer to the Federal Register notice Shiga Toxin-Producing Escherichia coli in Certain Raw Beef Products | PDF). These six non-O157 STECs are O26, O45, O103, O111, O121, and O145.

On June 4, 2012, FSIS began verification testing for these non-O157 STEC in domestic and imported beef manufacturing trimmings from cattle slaughtered on or after June 4, 2012. Beef manufacturing trimmings collected from cattle slaughtered before June 4, 2012, or that contain other components such as cheek meat are analyzed for E. coli O157:H7 only.