Your browser does not support JavaScript! Fruit and Vegetables Archives ⋆ The BioExpert

Search Results


The Latest Update in the E. coli romaine lettuce outbreak from FDA and CDC


Outbreak update

Lettuce irrigationUpdate reports from both the CDC and the FDA summarized the status of the outbreak after its conclusion. As of June 27, 2018, the human toll from the romaine lettuce outbreak was: 210 people infected with the outbreak strain of E. coli O157:H7, 96 hospitalized, 27 developed hemolytic uremic syndrome, and 5 deaths were reported from 36 states. The most recent victim became sick on June 6.
In an evaluation of the environment in the Yuma growing area, including water, soil, and manure, the CDC laboratory identified the outbreak strain of E. coli O157:H7 in water samples taken from a canal in the Yuma growing region. Additional strains of Shiga-toxin producing E. coli were found in the water samples, but initial testing of these isolates indicates they are different than the outbreak strain.   
The authorities did not reveal the canal location or how the bacteria got into the canal. In a statement by Scott Gottlieb, M.D., FDA Commissioner, he said that “More work needs to be done to determine just how and why this strain of E. coli O157:H7 could have gotten into this body of water and how that led to contamination of romaine lettuce from multiple farms.” They also did not discuss why it took them so long to test an obvious source of contamination, such as the irrigation water.
The CDC used whole genome sequencing (WGS) that provided fingerprints for pathogens was used to analyze 184 isolates from ill consumers. They found that the E. coli O157:H7 causing the outbreak was resistant to chloramphenicol, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole.  Isolates from four of those ill people also contained genes for resistance to ampicillin and ceftriaxone. However, these resistances do not impact patients since these antibiotics are not recommended for treatment of E. coli O157 infections.
CDC and FDA need to do more work to determine just how and why this strain of E. coli O157: H7 could have gotten into this body of water and how that led to contamination of romaine lettuce from multiple farms. 

New techniques make the investigation more efficientE. coli outbreak

In his statement, Scott Gottlieb, FDA commissioner, praised the work of the CDC during this outbreak and the utilization of new technologies such as WGS claiming “What’s happening is that our ability to identify outbreaks has dramatically improved due to new information technologies and laboratory techniques. “
Dr. Gottlieb said “Despite our best efforts to ensure the safest food supply possible, foodborne illness continues to occur in the U.S. and elsewhere around the globe. In the U.S., CDC — the agency that primarily detects multi-state outbreaks of illness — estimates that foodborne illness affects nearly 50 million people annually, which is about one in six Americans. Of these, an estimated 128,000 people are hospitalized, and 3,000 die each year. These numbers are tragically high… We need to take additional steps, and do it faster, to improve the safety of our food supply. “
He promised that”When appropriate and available, we’ll release information on retail outlets where contaminated foods may have been purchased if this information can quicken a recall or help a consumer better identify a product.” as was done with pre-cut melon.
Missing from this discussion is the need for better tracking mechanisms that will allow the FDA and food manufacturers and processors to quickly identify the source of an outbreak and remove the products from the shelves.
Finally, Dr. Gottlieb said, “I remain committed to investing in FDA’s food program, and building on its success — and to applying the FDA’s food safety expertise to protect American families and keep them safe.” 

Should tracing the source of the E. coli O157:H7 in lettuce be a top priority?

Almost three months after the outbreak started, consumers, the food industry, the government agencies (CDC and FDA) are getting antsy because the source of contamination for the E. coli O157: H7 in lettuce is still unknown.  Most of the focus is currently on traceability. Should the focus be there?

The human toll

This outbreak took a huge human toll.  According to an update by the CDC by now, 197 people from 35 states were infected with the outbreak strain of E. coli O157:H7.   48% of them have been hospitalized, including 26 people who developed hemolytic uremic syndrome; five deaths have been reported from Arkansas (1), California (1), Minnesota (2), and New York (1).
The CDC emphasizes that most of the newly reported cases involve people who fell ill two to three weeks ago, when contaminated lettuce from the Yuma, Arizona, area was still available to consumers. Some people also got sick after “close contact” with infected individuals. It is important to accentuate that most people got sick before the CDC announcement not to eat romaine lettuce from Yuma.

The economic Toll

Beyond the human suffering, the E. coli outbreak caused enormous losses to growers, retailers, and disrupted supply chains as restaurants scrambled to find romaine lettuce alternatives. “During the week of April 14 (the week the news broke), romaine dollar sales fell 20%, which pushed total lettuce performance down by double digits: iceberg lettuce dollar sales were down 19%; red leaf lettuce dollar sales fell 16%; and endive dollar sales dipped 17%,” according to a Nielsen report on National Salad Month.
In May, Romaine sales fell nearly 45%, according to the WSJ, iceberg fell 22%, and red leaf fell 17%. Prices for whole heads of romaine lettuce were down 60%. This deadly outbreak had shaken consumer’s confidence in leafy greens and especially lettuce, resulting in millions of dollars of losses for growers, retailers, and restaurants.”

The letter from consumer groups to FDA

After two outbreaks of E. coli O157: H7 in lettuce, that both went unsolved, 9 consumer and food safety groups (Center for Foodborne Illness Research & Prevention; Center for Science in the Public Interest; Consumer Federation of America; Consumers Union; Food & Water Watch: National Consumers League; The Pew Charitable Trusts; STOP Foodborne Illness; and the Trust for America’s Health.) wrote a letter to FDA Commissioner Scott Gottlieb  In the letter, the organizations demand that FDA should add regulations within the next six months “for comprehensive and rapid traceability of produce, including leafy greens.”
In the letter they claim that existing recordkeeping requires only “one step forward, one step back” records that result in “tangled web of inconsistent and inadequate” information for those tracking outbreaks. They claim that “Part of the purpose of this (FSMA) landmark legislation was to enhance traceability in the event of an outbreak of foodborne illness, allowing the FDA to trace back illness to its source and implement swifter and more accurate recalls.”  “The repeated outbreaks linked to produce and leafy greens since passage of FSMA leave no doubt that these products belong in the “high-risk” category. “
The primary focus of this letter is an improvement of traceability of the lettuce suggesting blockchain as one of the options.

FDA effort to trace the source

On May 31, Scott Gottlieb, M.D. Commissioner of the FDA, and Stephen Ostroff, M.D FDA’s Deputy Commissioner issued an update on the traceback efforts to find the source of the  E. coli O157:H7. This investigation includes the study of the multiple steps (suppliers, distributors, and processors cutting the lettuce, and bagging it). It starts at the farm and ends at the bags, attempting to accurately follow the pass of the contaminated lettuce to the supermarket, restaurant or other location where it was sold or served to consumers that got sick. 
The traceback efforts intend to find points of convergence from several well-identified clusters of illness with a common point of exposure, such as a supermarket or restaurant. A line is drawn for each cluster from one point in the supply chain to another point.  Intersections in the line can lead back to a common location that might be the source of contamination.
As can be seen in the diagram below there are no obvious points of convergence along the supply chain. The exception is whole head lettuce served in the Alaska correctional facility (see the middle of the chart).  The reason for the easy traceback is that it was not processed and was not mixed with lettuce from multiple farms.
Figure 1: traceback diagram for FDA investigation of multistate outbreak of E. coli O157:H7 infections linked to romaine lettuce from Yuma growing region.
The data indicates that there is no simple explanation on how the outbreak occurred. It also indicates that the contamination happened in the Yuma growing area and not later. They speculate that “contamination occurred on multiple farms at once, through some sort of environmental contamination (e.g., irrigation water, air/dust, water used for pesticide application, animal encroachment).” Dr. Gottlieb and Dr. Ostroff acknowledge that the source of contamination might be challenging to find.

Is blockchain and traceability the solution?

As explained in a previous blog a bag of lettuce might contain pieces of lettuce from more than one farm, making tracing a piece of lettuce to a particular farm very difficult. The efforts by FDA to trace back to the source demonstrate the challenges.
Even if we had a perfect traceback system, it might not have helped significantly in preventing the outbreak. Since it takes a couple of weeks to identify that there is an outbreak, by the time that CDC and FDA realized that there is an outbreak related to lettuce most of the ill people had already consumed the product.
“If they (FDA) know the points of sale, why not say so,” said William Marler. According to Bill Marle  “there are at least four separate clusters, the one in Alaska linked to Harrison Farm, one on the East Coast linked to Panera Bread and Freshway, and two on the West Coast linked to Papa Murphy’s and Red Lobster.” He is working to file lawsuits against the place of purchase of the contamination of the romaine to force the disclosure of distributors that sold the contaminated lettuce.

Where to Focus?

A new task force has been initiated to improve food safety around leafy greens, Scott Horsfall, CEO of the California Leafy Greens Marketing Agreement and a member of the task force steering committee said: “There’s been a recognition that the industry … and the science community and all the stakeholders in this effort need to come together again and take a good, hard look at everything that is available and see if we can’t figure out what steps can be taken so that we reduce the risk of this kind of thing happening again,” he also quoted Horsfall. “I would say that we’re going to focus heavily on practices that are going to prevent illnesses in the future because traceback and the investigation often just take a long time, so far better if we prevent the pathogens from ever getting in the marketplace.”
Perhaps scientists from academia, farmers, and other experts from all over the country should be tasked with solving the contamination problem rather than merely the traceability issue.

Cyclospora Infections are up this Summer Sickening Nearly a 1,000 Persons in 36 States


The CDC Report

The CDC reported that since the beginning of 2017 to mid-September there have been 988 Laboratory confirmed cases of Cyclospora infected people in 36 states of the USA. The number of cases this year is significantly higher than in 2016.
The states with the most cases are Texas 28.8%, Florida 12.0%, and New York (including NYC) 10.6%.

Historical View

While the number of cases is higher this year, the director of CDC’s Division of Parasitic Disease, Dr. Monica Parise, said: “The numbers from this year were probably not outside the range that we’ve seen for the last five years,” According to Parise the numbers last year were low.
The CDC claims that it is not unusual to see an increase in Cyclospora infection in the US between May and September. However, as the table shows the increase this year seems to be outside the norm.   In the last decade, only in 2005, the number of cases came close to this year, with 582 people sick in Florida. The outbreak source was identified as basil from Peru.

Reason for the Outbreak

Currently, no specific product has been connected to the infections, and it is unclear if the various cases in the different states are related to each other. The specific vehicles of the infections have not been identified and the sources are being investigated. The CDC report claims that “It is too early to say whether cases of Cyclospora infection in different states are related to each other or to the same food item(s).”

The EPI Curve

The EPI curve shows the progression of illnesses in an outbreak over time. It shows when people become ill by day. There is an inherent delay between the date that an illness starts and the date when the case is reported to public health authorities.  For the Cyclospora outbreaks in 2017, the following curve was generated by the CDC
*N=553. Data are current as of 9/13/17.  These cases occurred in persons with no history of travel outside of the United States or Canada in the 14 days before onset of illness. Illnesses that began after Aug. 2 may not yet have been reported to CDC because of the lag time between a victim’s first doctor visit, lab tests, paperwork and finally reports being filed with public health agencies. 


Cyclosporiasis is an intestinal illness caused by the unicellular parasite Cyclospora cayetanensis. According to the CDC, People can become infected with Cyclospora by consuming food or water contaminated with the parasite.
The oocysts shed in the feces of infected persons must sporulate outside the host, to become infective for another person. Therefore, it is not transmitted usually from person to person, but through food or water. The sporulation process requires days to complete.
Cyclospora is by and large found in tropical and subtropical countries. It is normally not killed by most chemical disinfectants.
Products that historically caused outbreaks include fresh produce: basil, cilantro, lettuce, raspberries and snow peas.


Why do we see a higher number of infections despite FDA preventative measures?
Due to a number of outbreaks traced to fresh cilantro from the region of Pueblo, Mexico, the FDA increased inspection and enforcement there. According to the FDA “Beginning in 2015, from April 1 through August 31, cilantro from this region has been and continues to be detained without physical examination at the U.S.-Mexican border and refused admission into the United States.”
The FDA suggested in September 2016 that the lower number of infections that year correlated with the first full season that the FDA’s Import Alert for fresh cilantro from Puebla was in effect. Therefore, the question should be asked why we see such an increase this year.

FDA Commissioner Announced a Four Year Delay in Implementing Some Produce FSMA Rules

In a speech in front of National Association of State Departments of Agriculture (NASDA), Dr. Scott Gottlieb, the FDA commissioner outlined some immediate steps to facilitate the implementation of the Produce Safety Rule established by the FDA Food Safety Modernization Act (FSMA).
Dr. Gottlieb claims that since being in his post, he gained a deeper appreciation for the challenges and complexity that the globalized farming community is facing.

Agricultural Water Compliance Dates

He announced that the FDA issued a proposed rule that, if finalized, would extend the compliance dates for the agricultural water requirements by an additional two to four years (for produce other than sprouts).  The new agricultural water compliance date the FDA is proposing for the largest farms is January 26, 2022. Small farms would have until January 26, 2023, and very small farms January 26, 2024.
Sprouts, because of their unique vulnerability to contamination, remain subject to applicable agricultural water requirements in the final rule and their original compliance dates. 
He agreed that “microbial quality standards for agricultural water are too complicated, and in some cases too costly, to be effectively implemented.” Dr. Gottlieb also announced that “our intention to explore ways to simplify our approach to make compliance less burdensome and less costly, while still being protective of public health.”
To give the agency and the farmers more time, he is issuing an extension in the compliance dates” for the agricultural water requirements of the produce rule for non-sprout produce by an additional two to four years. This way the earliest non-sprout compliance date for the water standards won’t be until January 2022.”
The proposed extension will give the agency time to take another look at the water standards to ensure that they are feasible for farmers in all regions of the country while protecting public health. The agency has also increased the number of methods that can be used for water testing in agricultural water.

Educational Efforts

Dr. Gottlieb declared that the agency has recognized a need for additional efforts to educate the produce industry and state regulatory agencies on the new produce safety requirements, and will continue its focus on training, guidance development, and outreach over the next year. This is particularly important since the nation’s farming community has not previously been subject to this kind of oversight.
The FDA plans to learn more from farmers, state regulatory partners and other stakeholders about the diverse ways water is used and ensure that the standards will be as practical and effective as possible for all farming operations, during the time extension afforded by the extension.

Produce Inspection

The State Produce Implementation Cooperative Agreement Program that supports 43 states in their development of produce safety programs was awarded $30 million. This funding is in addition to on the nearly $22 million that FDA awarded last year to 42 states to develop produce programs and provide training and technical assistance.
Dr. Gottlieb assured the audiences that routine inspections would not begin until 2019. The additional time should be used to focus on issuing guidance that will be helpful to regulators and farmers.

On Farm Readiness Reviews

The farm readiness review is a voluntary program, where the farms are visited by a team of state officials, cooperative extension agents, and FDA produce experts.  The purpose of the visit is to give the farmers information about their readiness to meet the program requirements. The program will also help the FDA to identify training gaps that will be needed to be filled.


Dr. Gottlieb claimed that through Produce Safety Alliance (PSA) 176 farmer training courses had been conducted in 36 states as of June of 2017. More than 1,000 trainers were trained in these courses. NASDA-FDA working group was formed to work on plans for training state and federal inspectors and is finalizing the training modules.
FDA is also working with NASDA to determine the best training platforms for ensuring that cooperative extension agents can have the training they need to be effective. Training of state regulators will be a top priority for the FDA in 2018.

Biofilm and food safety: What is important to know?


Part 2: What are the best control strategies?

Dr. Bassam A. Annous, Eastern Regional Research Center, USDA–ARS–NEA, and Dr. Ruth Eden, BioExpert.
Biofilms are usually formed in a wet environment and in the presence of nutrients.  Once biofilms are formed, the cleaning of the food and food contact surfaces becomes more difficult to remove the extracellular polymeric substances (EPS). Therefore, prevention of biofilm formation, using regularly scheduled cleaning and disinfecting protocols is an important first step in preventing cells from attaching and forming biofilms on surfaces.
High-temperature washing can reduce the need for the physical force required to remove biofilms. Chemical cleaners suspend and dissolve food residues by decreasing surface tension, emulsifying fats, and denaturing proteins. The mechanism by which cleaning agents remove EPS associated with biofilms has not been determined.

Fruit and Vegetable Surfaces

Conventional methods of washing fresh produce with hypochlorite or other sanitizing agents cannot assure microbial safety because they can only achieve 1-2 log reduction. This is because of many enteric pathogens, such as Escherichia coli O157:H7, cause illness at very low infectious doses. For apples, using water, detergents or sanitizing agents, produced a maximum of 3-log (99.9%) reduction in the levels of E. coli. The same treatment using brush washer surprisingly gave less than a 1-log (90%) reduction in E. coli.
A commercial-scale surface pasteurization treatment developed at ERRC (Annous, Burke, and E. Sites), resulted in 4-log (99.99%) reduction in the population of Salmonella Poona on the surface of artificially contaminated cantaloupe. The process involved the immersion of melons in water at 168.8°Fahrenheit for three minutes and then rapidly cooling them. This pasteurization process not only enhances the safety of the fruit but increases the product shelf life by reducing the native microflora that may cause spoilage.


Bacterial cells could attach and form biofilms on food processing equipment.  The complexity of processing equipment makes it difficult to remove and/or inactivate the bacterial cells in biofilms on food processing surfaces.  Since it is extremely difficult to remove these biofilms, food processors should prevent biofilm formation in the first place. This could be done by developing and maintaining a thorough sanitation regiment to help prevent a biofilm layer from attaching to equipment surfaces. Product residues due to spills or debris in the facility support bacterial proliferation and subsequent biofilm formation. Consequently, regular removal of food residues is a key to preventing biofilm formation.
Oko, 2013 suggested three important steps to removing biofilm in a food processing facility:
(i)     Cleaning with appropriate sanitizing agents at the required concentrations
(ii)     Allowing enough exposure time at the appropriate temperature
(iii)     Applying mechanical action
This combination is claimed to penetrate and/or remove the biofilm, and thereby to kill the embedded bacterial cells.
An effective cleaning procedure would break up or dissolve EPS allowing sanitizers to gain access to viable bacterial cells. Alkaline cleaners, especially those with chelators like EDTA, are more effective at removing biofilms than acidic cleaners. Bacteria become far more susceptible to sanitizers once the biofilm matrix has been destroyed, certain enzymes have been proven effective in disrupting EPS matrixes, thus allowing for the removal of biofilms. Recently, novel methods that can serve as alternatives to the current methodology for the disinfection of microbial contamination, such as essential oils and bacteriophages have been successfully tested.
Poly ethylene glycol (PEG) has been shown to inhibit protein adsorption and bacterial attachment to surfaces.  Cold plasma was used to deposit PEG-like structures on the surfaces of stainless steel 304 and 316L using 12-crown-4 ether and tri (ethylene glycol) dimethyl ether (triglyme), and ethylene glycol divinyl ether as starting materials.
The plasma modified surfaces significantly reduced biofilm formation by about 80%. When 1% beef hot dog was added to the base medium, biofilm formation on stainless steel 304 was reduced further. Plasma modification of the surfaces did not interfere with the efficacy of cleaning by the chlorinated alkaline detergent.
Newer physical methods of biofilm removal include super-high magnetic fields, ultrasound treatment, high pulsed electrical fields, combined use of high pulsed electrical fields in conjunction with organic acids, and low electrical fields alone or in combination with biocides, such as silver, carbon, platinum, and antibiotics.


Most bacterial cells in nature exist in biofilms instead of planktonic single cells.  Organic and inorganic material (nutrients) attach to surfaces of food and/or equipment and thus creates a conditioning layer whereby microorganisms attach to. Microbial cells then start secreting EPS that further help in the attachment of the biofilm to the food and food processing surfaces.  The ESP formation acts as a barrier from sanitizing compounds, making the biofilm stronger. Bacterial activity within the biofilm community can be coordinated through cell-to-cell signaling (Quorum sensing).
Biofilm formation is associated with many foodborne outbreaks. As a result, biofilm has become a problem in food industries as it renders its inhabitants resistant to antimicrobial agents and cleaning agents. The growth of biofilms in food processing environments leads to an increased opportunity for microbial contamination of the processed product.  Pathogenic microorganisms in biofilms are the major source of food contaminations.
Biofilms were created by various bacteria on fruit and vegetable surfaces, on various meats, and especially on all types of processing equipment.  Once created the biofilm is very difficult to remove, and offer significant protection to the bacteria residing in it.
Breaking up EPS is important in eliminating the biofilm protection and making the bacterial cells more susceptible to the cleaning sanitizers.  Several novel methods are available to better clean surfaces containing bacteria in biofilms.

The Papaya Salmonella Outbreak Expands as Number of Victims Triples


The Recalls

Since our last report on July 23, there have been several additional recalls associated with the outbreak of Salmonella in papayas. On July 26 after many people got sick, Grande Produce issued a recall for its imported papayas from the Carica de Campeche farm in Mexico. This farm seems to be the primary source of the outbreak. 
On August 4, a second papaya recall was issued by Agroson’s LLC, for more than 2,000 boxes of Cavi-brand Maradol Papaya imported from the same Mexican farm. A few days later, a third papaya recall was issued by Freshtex Produce. These papayas sold under the Valery brand were distributed in Illinois.
Carica de Campeche farm produced papayas under the following brands: Caribeña, Cavi, and Valery.
The FDA first recalled the Maradol papayas from the Carica de Campeche farm in Mexico.
Carica de Campeche farm under the brand Caribeña: This first recall came after extensive testing and trace back.  Papayas from the Carica de Campeche farm tested positive for Salmonella Kiambu, Salmonella Thompson, Salmonella  Agona,  Salmonella Senftenberg, and Salmonella Gaminara. The Caribeña brand was distributed by Grande Produce between July 10 and 19, 2017.
Cavi brand papayas distributed by Agroson’s:  Agroson’s LLC, recalled certain Maradol Papaya Cavi Brand, grown and packed by Carica de Campeche.  The papayas were distributed on July 16-19 and were available to consumers until July 31. No illness has been reported due to the Maradol Papaya Cavi Brand, and the recall was voluntary in cooperation with the FDA.
Valery brand distributed by Freshtex: The FDA announced that Freshtex Produce of Alamo, TX was voluntarily recalling “Valery” brand Maradol Papayas grown and packed by Carica de Campeche. The papayas were distributed to the State of Illinois from July 10 to July 13, 2017. No illness has been reported.
The FDA increased its testing to see if papayas from other farms from Mexico could be contaminated. More brands and distributors are expected to be linked to the investigation.

The Outbreak

The CDC found that as of August 9 a total of   141 people were infected with the outbreak strains of Salmonella Kiambu (51) or Salmonella Thompson (90) in 19 states. Among 103 people with available information, 45 (44%) have been hospitalized.
The data from the testing laboratory and from epidemiological investigation indicated that the most likely source of the outbreak was Maradol papayas from Carica de Campeche farm in Mexico.

Why did it Happen?

Papayas from Mexico are being screened at the border for Salmonella since the outbreak in 2011, by a third party laboratory. Only papayas that have tested negative for Salmonella are allowed into the USA.  The question needs to be asked: how was it possible that the contaminated papayas were able to get into the USA?
As shown in our recent post, research indicated that bacteria can attach and colonize on the surfaces of plants, ultimately forming biofilms. Bassam A. Annous 2005  shows Salmonella produces fimbriae and cellulose, commencing biofilm formation, which helps Salmonella attach and colonize on melon and cantaloupe surfaces. Once attached the cells survive better on the surface.
As mentioned in our previous post, the outbreaks can be due to the ability of Salmonella to attach or internalize into fruits.  Survival and multiplication of Salmonella on fresh fruits is considerably increasing once the protective epidermal barrier has been broken.    FSMA is designed to help minimize the risk of illness from foodborne pathogens in fresh fruits, and include requirements for water quality, employee hygiene, and equipment and tool sanitation. However, to date, all these new measures did not prevent the current papaya outbreak.