Careful with that cookie dough: E. coli O157:H7 can survive in wheat (at least in the lab)

Escherichia coli O157:H7 is a human pathogen that can cause bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. E. coli O157:H7 illnesses are mainly associated with undercooked beef; however, in recent years, outbreaks have been linked to fresh produce, such as spinach, lettuce, and sprouts. 2009, flour was implicated as the contamination source in an outbreak involving consumption of raw cookie dough that resulted in 77 illnesses. The objectives of this research were to determine (i) whether E. coli O157:H7 could be translocated into the internal tissues of wheat (Triticum aestivum) seedlings from contaminated seed, soil, or irrigation water and (ii) whether the bacterium could survive on flowering wheat heads. The levels of contamination of kanamycin-resistant E. coli O157:H7 strains in seed, soil, and irrigation water were 6.88 log CFU/g, 6.60 log CFU/g, and 6.76 log CFU/ml, respectively.

One hundred plants per treatment were sown in pot trays with 50 g of autoclaved soil or purposely contaminated soil, watered every day with 5 ml of water, and harvested 9 days postinoculation. In a fourth experiment, flowering wheat heads were spray inoculated with water containing 4.19 log CFU/ml E. coli O157:H7 and analyzed for survival after 15 days, near the harvest period. To detect low levels of internalization, enrichment procedures were performed and Biotecon real-time PCR detection assays were used to determine the presence of E. coli O157:H7 in the wheat, using a Roche Applied Science LightCycler 2.0 instrument.

The results showed that internalization was possible using contaminated seed, soil, and irrigation water in wheat seedlings, with internalization rates of 2, 5, and 10%, respectively. Even though the rates were low, to our knowledge this is the first study to demonstrate the ability of this strain to reach the phylloplane in wheat. In the head contamination experiment, all samples tested positive, showing the ability of E. coli O157:H7 to survive on the wheat head.


Transmission of Escherichia coli O157:H7 to internal tissues and its survival on flowering heads of wheat


Journal of Food Protection®, Number 3, March 2015, pp. 484-627, pp. 518-524(7)

Martinez, Bismarck; Stratton, Jayne; Bianchini, Andréia; Wegulo, Stephen; Weaver, Glen

Market impacts of E. coli vaccination in US feedlot cattle

Immunization through vaccination has been a commercially available pre-harvest intervention to reduce E. coli shedding in cattle for about five years.

Despite demonstrated substantial improvement in human health that vaccine adoption offers, it has not been widely adopted. This highlights the need for understanding the economic situation underlying limited adoption.

Using an equilibrium displacement model, this study identifies the economic impact to U.S. feedlots implementing this vaccination across a series of alternative scenarios.

Producers face $1 billion to $1.8 billion in welfare losses over 10 years if they adopt this technology without any associated increases in demand for fed cattle. Retail beef demand increases of 1.7% to 3.0% or export demand increases of 18.1% to 32.6% would each individually make producers economically neutral to adoption. Retail or packer cost decreases of 1.2% to 3.9% would likewise be sufficient to make producers neutral to adoption.

Agricultural and Food Economics 2015, 3:7

Glynn T Tonsor and Ted C Schroeder

Minnesota vs. California: Investigators can’t identify source of E. coli O157 outbreak; celery or caterers suspected

The root of last summer’s E. coli outbreak linked to California grown celery remains a mystery. After six months of inspections and testing, investigators found no local sources of E. coli contamination – good news for Salinas Valley growers and packers.

celery.farmExcept testing proves not much.

Last July, 57 people were sickened and nine were hospitalized in Minnesota with E. coli O157:H7. All of the victims ate celery or potato salad made with celery at events catered by the same company. Government investigators traced the celery to Martignoni Ranch just north of Gonzales, grown by Costa Farms of Soledad. The celery was cooled and packed by Mann Packing in Salinas.

An attorney representing the victims believes the E. coli contamination started with the caterer, not the growers or packers.

“This report will help get the case resolved,” said William Marler, managing partner of the Marler Clark law firm in Seattle. “We believe the caterer is likely to settle,” he said, since the company won’t be able to point the finger at anyone else.

In late January, the California Department of Public Health completed its initial inquiry into the incident, which state officials conducted in cooperation with the federal Food and Drug Administration. Investigators found no E. coli in seven soil and water samples taken from the ranch. During their inspection, they didn’t see any problems that might have contributed to cross-contamination. And the investigators could not find signs of contamination from a defunct dairy operation next door.

Draft guidance to help evaluate effectiveness of drugs to reduce pathogenic Shiga toxin-producing E. coli in cattle

The U.S. Food and Drug Administration issued today draft Guidance for Industry #229: Evaluating the Effectiveness of New Animal Drugs for the Reduction of Pathogenic Shiga Toxin-Producing E. coli (STEC) in Cattle. GFI #229 provides recommendations on study design and criteria drug manufacturers should use when evaluating the effectiveness of animal drugs intended to reduce STEC. The draft guidance addresses topics including:

supershedder.e.coliprotocol development;

study conduct;

animal welfare;

nutritional content of experimental diets;

the assessment of drug concentrations in experimental diets;

experimental parameters; and

substantial evidence of effectiveness.

The draft guidance also provides recommendations for acceptable indications, as well as study designs and analyses that sponsors should use to verify the effectiveness of drugs intended to reduce pathogenic STEC in cattle.

STEC is a foodborne pathogen found mostly in cattle, but can cause serious human illness if contracted. In the U.S., E. coli O157:H7 is the most common type of STEC associated with foodborne E. coli outbreaks, but other serotypes of STEC may also cause illness in people. Most foodborne E. coli infections can be prevented by thorough hand washing, cooking meats to the appropriate temperature, and preventing cross contamination in food preparation.

The FDA is accepting public comments on this draft guidance beginning on February 24, 2015. To submit your comments electronically to the docket, go to and type FDA-2015-D-0235 in the search box. Please note that the docket will not be open to accept comments until this date. The comment period will close 60 days after it publishes in the Federal Register. While comments are welcome at any time, you should submit them by the closing date for the FDA to consider your comments in drafting the final guidance.


We’re all hosts on a viral planet: E. coli O157 edition

A novel phage, Φ241, specific for Escherichia coli O157:H7 was isolated from an industrial cucumber fermentation where both acidity (pH ≤ 3.7) and salinity (≥5% NaCl) were high.

phageThe phage belongs to the Myoviridae family. Its latent period was 15 min and average burst size was 53 phage particles per infected cell. The phage was able to lyse 48 E. coli O157:H7 strains, but none of the 18 non-O157 strains (including E. coli O104:H7) or the 2 O antigen-negative mutants of O157:H7 strain, 43895Δper (also lacking H7 antigen) and F12 (still expressing H7 antigen). However, the phage was able to lyse a per-complemented strain (43895ΔperComp) which expresses O157 antigen.

These results indicated that phage Φ241 is specific for O157 antigen, and E. coli strains lacking O157 antigen were resistant to the phage infection, regardless of the presence or absence of H7 antigen. SDS-PAGE profile revealed at least 13 structural proteins of the phage.

The phage DNA was resistant to many commonly used restriction endonucleases, suggesting the presence of modified nucleotides in the phage genome. At the multiplicity of infection of 10, 3, or 0.3, the phage caused a rapid cell lysis within 1 or 2 h, resulting in 3.5- or 4.5-log-unit reduction in cell concentration. The high lytic activity, specificity and tolerance to low pH and high salinity make phage Φ241 a potentially ideal biocontrol agent of E. coli O157:H7 in various foods. To our knowledge, this is the first report on E. coli O157:H7 phage isolated from high acidity and salinity environment.

 Escherichia coli O157:H7 bacteriophage Φ241 isolated from an industrial cucumber fermentation at high acidity and salinity

Frontiers in Microbiology, 17 February 2015 [ahead of print]

Zhongjing Lu and Fred Breidt

Up the butt: Clearance of E.coli O157:H7 infection in calves by rectal administration of bovine lactoferrin

Enterohemorrhagic Escherichia coli (EHEC) strains, of which E. coli O157:H7 is the best-studied serotype, are an important group of foodborne pathogens causing severe illness in humans worldwide.

calfThe main reservoirs for EHEC are ruminants, mostly cattle, which harbor the bacteria in their intestinal tracts without showing clinical symptoms. In this study, we used bovine lactoferrin, a natural occurring bactericidal and immunomodulating protein, as an antibacterial agent against EHEC infection in cattle.

Nine 3-month-old Holstein-Friesian calves were experimentally infected with EHEC (strain NCTC12900). Three animals received a daily rectal spray treatment with bovine lactoferrin, three animals received an oral treatment, and three animals served as a control group. Blood samples were collected weekly and fecal samples twice weekly to monitor antibody responses and fecal excretion, respectively. Animals in the rectal group ceased shedding within 26 days of the experimental treatment and remained negative. This beneficial effect of bovine lactoferrin was not observed in the oral group, where animals were still shedding at the time of euthanasia (day 61). All groups developed serum responses, but no clear differences could be observed between the groups. However, the results indicate that the use of bovine lactoferrin as a rectal treatment can be a useful strategy to preclude further transmission of EHEC infections from cattle to humans.

Clearance of Escherichia coli O157:H7 Infection in calves by rectal administration of bovine lactoferrin

Applied and Environmental Microbiology

Kieckens E, Rybarczyk J, De Zutter L, Duchateau L, Vanrompay D, and Cox E

Perspectives on super-shedding of Escherichia coli O157:H7 by cattle

Escherichia coli O157:H7 is a foodborne pathogen that causes illness in humans worldwide. Cattle are the primary reservoir of this bacterium, with the concentration and frequency of E. coli O157:H7 shedding varying greatly among individuals.

supershedder.e.coliThe term “super-shedder” has been applied to cattle that shed concentrations of E. coli O157:H7≥104 colony-forming units/g feces. Super-shedders have been reported to have a substantial impact on the prevalence and transmission of E. coli O157:H7 in the environment. The specific factors responsible for super-shedding are unknown, but are presumably mediated by characteristics of the bacterium, animal host, and environment.

Super-shedding is sporadic and inconsistent, suggesting that biofilms of E. coli O157:H7 colonizing the intestinal epithelium in cattle are intermittently released into feces. Phenotypic and genotypic differences have been noted in E. coli O157:H7 recovered from super-shedders as compared to low-shedding cattle, including differences in phage type (PT21/28), carbon utilization, degree of clonal relatedness, tir polymorphisms, and differences in the presence of stx2a and stx2c, as well as antiterminator Q gene alleles. There is also some evidence to support that the native fecal microbiome is distinct between super-shedders and low-shedders and that low-shedders have higher levels of lytic phage within feces.

Consequently, conditions within the host may determine whether E. coli O157:H7 can proliferate sufficiently for the host to obtain super-shedding status. Targeting super-shedders for mitigation of E. coli O157:H7 has been proposed as a means of reducing the incidence and spread of this pathogen to the environment. If super-shedders could be easily identified, strategies such as bacteriophage therapy, probiotics, vaccination, or dietary inclusion of plant secondary compounds could be specifically targeted at this subpopulation.

Evidence that super-shedder isolates share a commonality with isolates linked to human illness makes it imperative that the etiology of this phenomenon be characterized.

Foodborne Pathogens and Disease. February 2015, 12(2): 89-103

Munns Krysty D., Selinger L. Brent, Stanford Kim, Guan Leluo, Callaway Todd R., and McAllister Tim A.

Canberra uses cow shares to get their raw milk fix

A Canberra woman admits “it would be fair to say that pasteurised milk would be safer” but she still intends on using raw milk for her family.

sprout.santa.barf.xmasSaffron Zomer developed a taste for raw milk while living overseas.

She is now involved in a cow share scheme which presently enables her to consume the untreated milk.

Ms Zomer is among around 25 Canberra households who are part of the scheme run by Julia McKay a dairy farmer at Bungonia north of the nation’s capital.

Ms McKay delivers around ten litres of milk on a weekly basis to the various shareholders.

Ms Zomer gets the milk “primarily because its delicious” after living in Switzerland where she and her husband had access to raw milk.

“I did some research and I think the nutritional value is higher.” Ms Zomer said.

Ms Zomer has three children, one who is newly born and not feeding on the milk.

“My oldest isn’t much of a milk drinker, but the little one likes it and he is always excited when it is delivery day because the milk is really fresh and he doesn’t like to drink supermarket milk anymore.” she observed.

Family guy barfShe argues that there is a clear difference in the taste of raw milk when compared to supermarket milk.

Her husband uses some of the milk to make cheese.

Ms Zomer compares drinking of raw milk to eating other unprocessed food.

“I also let my kids eat seafood, sprouts and raw spinach and chicken.

I wouldn’t let my kids eat raw sprouts. Or raw milk.

Washington firm recalls boneless beef trim product due to possible E. coli O157:H7 contamination

Washington Beef, LLC, a Toppenish, Wash., establishment, is recalling 1,620 pounds of boneless  beef trim product that may be contaminated with E. coli O157:H7, the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) announced today.

Beef-Trimmings-85-15The following boneless beef product produced on Nov. 28, 2012, is subject to recall:

  • 60 lb. bulk packs of “TRIM 65/35 (FZN)”        

The product subject to recall bears the establishment number “EST. 235” inside the USDA mark of inspection.

The problem was discovered during an internal records audit by the company, which notified FSIS. Product was shipped for further processing to a single grinding facility, then on for use in hotels, restaurants and institutions in Oregon and Washington.         

FSIS and the company have received no reports of illnesses associated with consumption of this product.

Cost-benefit analysis for USDA FSIS’ implementation of its non-O157 STEC testing

FSIS has estimated the cost to the regulated industry and FSIS associated with the implementation of its non-O157 STEC testing on beef manufacturing trimmings, based on Agency testing data and information collected through the FSIS 2013 Pathogen Controls in Beef Operations Survey.

cost.benefitWe also assessed the benefits associated with the new testing. In addition, we estimated the cost and examined benefits of expanding its non- O157 STEC testing to ground beef and ground beef components other than beef manufacturing trimmings. The Agency concludes that the costs for sampling and testing are low and believes that the benefits justify the costs. However, FSIS was not able to quantify the benefits of expanding the testing.