January,
2007
The
E. coli Outbreak — Lettuce Learn a Lesson
By Sharon Palmer, RD
Today’s Dietitian
Vol. 9 No. 1 P. 28
There are initiatives in place to guard
against it—yet contaminated produce led to cases of illness
and death. Are food safety regulations too soft or is it a matter
of noncompliance?
When the E. coli O157:H7 breakout related to
fresh spinach hit the news last fall, it hit big. If people
were looking for an excuse not to eat their dark, leafy greens,
now they had one. Although people have grown accustomed to being
buffeted by food poisoning reports on the evening news, this
particular outbreak really hit home.
The sheer scope of the spinach outbreak was
undeniable. An estimated 51 cases of illnesses per outbreak
are linked with produce.1 This outbreak was roughly four times
that size. People wondered for weeks how something as supposedly
healthy as fresh spinach could cause illness and death. In a
survey by NBC11—which serves San Jose, San Francisco,
and Oakland, Calif.—21% of voters to date have indicated
that they will never eat spinach again unless it is locally
grown.2
The FDA traced the spinach outbreak that sickened
204 people and killed three to four fields on four ranches located
in Monterey and San Benito counties in California where the
spinach was grown by third-party growers. The FDA reported on
September 29, 2006, that all spinach implicated in the outbreak
was traced back to the company Natural Selection Foods of San
Juan Bautista, Calif.
Not Just a Meat Problem
While our food safety focus has often centered on the processing
and handling of raw meat and poultry, this outbreak opened our
eyes to a new era of food-borne illness dawning on produce farms.
The fact that some consumers open bags of prewashed and prechopped
fresh greens and dump them onto their dinner plates without
cooking or washing them further increases the gravity of the
situation.
For many, the E. coli outbreak in spinach came
as no surprise. Since 1998, the FDA has warned fruit and vegetable
producers about the potential of E. coli O157:H7 contamination.
A previous outbreak in October 2003 involving fresh spinach
and E. coli O157:H7 contamination in California resulted in
16 cases of illness and two deaths.
“Fresh produce was not a big source of
food-borne illness. It was typically associated with meat items,
but now the discussion is on fresh fruits and vegetables. It
sounds an alarm for everyone in food safety practices,”
says John Krakowski, MA, RD, CDN, a food safety coach in Flanders,
N.Y. An approximate 29% reduction in the number of E. coli O157:H7
cases has occurred since 1996 to 1998, thanks to measures targeting
ground beef safety and Hazard Analysis and Critical Control
Point (HACCP).3
“The general impression among experts
in the field is that the number and seriousness of outbreaks
is greatest in produce, sprouts, and juices,” says Charles
Benbrook, chief scientist at The Organic Center in Enterprise,
Ore. The Organic Center recently published a Critical Issue
Report on E. coli O157:H7 that discusses its relationship to
agriculture.
Under the Microscope
There are more than 225 unique strains of E. coli and the majority
of them are not dangerous. E. coli bacteria are essential to
the healthy functioning of human and animal digestive systems,
but some types have picked up extra genetic material that can
turn harmless bacterium into a threat. E. coli O157:H7 is among
the most dangerous strains when people are exposed to it. E.
coli O157:H7 doesn’t harm cattle because it does not bind
to the walls of their gastrointestinal tract. In humans, the
bacterium causes diarrhea that is often bloody and can be accompanied
by abdominal cramps or fever. Symptoms usually occur within
two to three days following exposure. Healthy adults can typically
shake E. coli O157:H7, but people at high risk, such as young
children and older adults, can develop hemolytic uremic syndrome,
which can lead to serious kidney damage and death.
E. coli O157:H7 is particularly pesky because
it survives heat, drying, and acidic conditions and causes infections
at very low doses. It has also been known to survive in soil
for up to six months. The first case of E. coli O157:H7 was
reported in 1975 and the first outbreak followed in 1982. The
8,598 cases associated with 350 outbreaks of E. coli O157:H7
reported to the Centers for Disease Control and Prevention from
1982 to 2002 accounted for less than one tenth of 1% of the
total number of cases during those years.4
E. Coli’s Link
to the Land
As investigators tracked down the source of E. coli O157:H7
contamination in fresh spinach, they discovered that all tests
performed on Natural Selection Foods processing facilities by
independent scientists and government investigators came up
clean, indicating that the E. coli contamination occurred in
the fields. The plant’s triple washing procedure didn’t
appear to successfully remove the E. coli O157:H7 from the spinach,
prompting food safety experts to realize that produce needs
to be clean at the time it enters processing.
Specific samples of cattle feces on one of the
implicated ranches tested positive based on the genetic fingerprints
for the same strain of E. coli O157:H7 responsible for the outbreak.
These results brought the whole connection of agriculture and
food safety from the shadows. Since E. coli can survive in soil,
water in troughs, and raw cattle manure for months, consider
the myriad ways it could find itself onto a wrinkly leaf of
spinach. The outbreak highlights how farming systems, cattle
and dairy cow manure, animal husbandry and feeding practices,
irrigation water quality, sanitation in field workers, fertilizers,
and agricultural regulations play into food safety.
Perhaps it was a red flag when cases of E. coli
O157:H7 illness were reported due to children being infected
at county fair petting zoos. Approximately 11% of the cattle
fecal samples tested for E. coli O157:H7 at Minnesota county
fairs in 2000 and 2001 tested positive.5
The Farm, an Open Environment
Farms are all about wide open spaces—you can’t seal
them off into sterile biospheres. Issues of previous land use,
adjacent land use practices, and water safety all come into
play. And then there’s that nagging problem of animal
waste from nearby livestock or even wildlife.
Krakowski points out, “Fruits and vegetables
are grown in nature’s restroom.” Agricultural experts
believe that even wildlife and birds may play a role in spreading
E. coli. Indeed, investigators found a positive match for E.
coli O157:H7 in the guts of a feral pig killed on the property
of one of the identified ranches where the strain was found.
There were signs that pigs had broken through a fence to eat
the spinach.
Although officials have not pinpointed feral pigs as the bacteria’s
carrier, this discovery has caused concerns about access of
wildlife to crops.
Enough Bugs to Go Around
Just ponder the many ways E. coli could rear its ugly head on
a farm and plenty of ideas pop into your head. “My first
thought when I heard about the spinach outbreak was: Did a farmer
change his [child’s] diaper … before heading to
the fields without first washing his hands?” says Amy
Barr, MS, EdM, RD, cofounder of Marr Barr Communications, a
strategic marketing and communications agency specializing in
food, nutrition, health, lifestyle, and sustainability. Officials
reported that the contamination route for the spinach outbreak
may have been via wandering livestock, substandard worker hygiene,
irrigation practices, or even wild boar.
One farming issue experts worry about is manure
practices. Benbrook reports that there are clearly problems
that arise as a result of manure lagoons and manure overflowing.
Dairy farms using concrete alleys and flushing systems were
eight times more likely to test positive for E. coli O157:H7
than other manure removal systems. Benbrook suggests improvements
can come from developing vegetative buffer strips along creeks
and irrigation canals and having healthy, biologically active,
organic soil with many different microbes that decrease pathogens
due to competition.
A study looking at E. coli O157:H7 cases in
Canada found that the application to cropland of raw manure
by a manure spreader or as liquid slurry was the second most
significant variable explaining the geographic distribution
of E. coli illnesses. (The strongest association was for the
ratio of cattle to humans.)6
“We always need to control any run-off
problems. Run-off can cause huge cross-contamination issues
around both big and small farms,” says Barr, who grew
up on a small farm in the Midwest and recently observed a farmer
in New England using a front-end loader to dump manure from
a barn onto his land with a stream running through it.
The manure problem flows right into another
big area of concern: water. The potential for irrigation ditches
and canals to be contaminated is a serious risk. We know contaminated
drinking water and water in lakes and pools have triggered cases
of illness linked to E. coli O157:H7 in the past.
“A big eye opener is water and how we
use water and take care of water. When we pollute water in one
part of the food system, it comes back to bite us in another
part—it is all connected,” says Alison H. Harmon,
PhD, RD, LN, assistant professor of food and nutrition and director
of the dietetics program at Montana State University and Sustainable
Agriculture and Food Systems cochair of the Hunger and Environmental
Nutrition Dietetic Practice Group.
The Great Cattle Debate
When samples of cattle fecal matter from one implicated ranch
from the spinach outbreak tested positive for the same strain
of E. coli bacteria that sickened people, the link between cattle
and crops became significant. The fecal matter specimens were
found one half mile to one mile from the produce field, which
abutted the livestock pastures.
Most of E. coli O157:H7 comes from the digestive systems of
beef and dairy cattle. Less than 1% to more than 10% of cattle
tested are found to shed E. coli O157:H7, which enters the environment
when it is shed in the manure of infected cattle. Once unleashed
in the environment, other animals can harbor it without apparently
suffering from it.
“It is clear that cattle on forage diets
are much less likely to shed E. coli O157:H7 in manure than
grain-fed cattle,” says Benbrook. When cows are fed high-energy,
grain-based diets, the pH in their digestive systems changes
to favor E. coli O157:H7. But Barr notes that while there’s
a lot to be said for avoiding feeding excessive amounts of grains
to ruminants, after frost and before spring greening ranchers
in most areas of the country can’t rely on pasture. “Snow
happens. Plus, most ‘pasture-based’ farmers, especially
dairy farmers, also supplement their livestock’s diets
with grain,” says Barr. “It’s not black and
white. If you feed cattle less grain, you’re not going
to eliminate E. coli.”
Some also argue that antibiotic use on livestock
fosters genetic mutations capable of turning generic E. coli
into a dangerous variant such as E. coli O157:H7. “It
is widely accepted that the antibiotics used in livestock accelerate
the rate of genetic adaptation in bacteria. The evidence is
overwhelming that antibiotics in pork and poultry lead to the
emergence of new antibiotic-resistant strains of bacteria,”
says Benbrook. “If there’s one antibiotic-resistant
gene somewhere in the environment, there are numerous ways to
get it into cattle. Agriculture has done far more than its fair
share to create antibiotic-resistant bacteria and further spread
it.”
Research has found varying levels of antibiotic
resistance in E. coli O157:H7 serotypes. A study on isolates
from cattle, humans, swine, and farms collected from 1985 to
2000 found that 39% of the E. coli isolates were resistant to
one or more antimicrobials.7
One Big Salad Bowl
Here’s a good question: Do people even think about where
the leafy greens came from before they rip into a pretty, cellophane
bag of precut salad purchased at their local supermarket? It
was a shock when the spinach outbreak highlighted the fact that
the spinach involved in making people sick in 26 different states
and Canada all came from Natural Selection Foods in the Salinas
Valley. To make matters worse, five other companies issued voluntary
recalls since their products may have contained spinach from
Natural Selection Foods. On top of that, Natural Selection Foods
has 20 other brands—from Earthbound Farm and Dole Food
Company, Inc. to Trader Joe’s and Sysco—that were
also recalled. Salinas Valley isn’t called the “nation’s
salad bowl” for nothing—75% of the country’s
fresh spinach comes from this region.
Jennifer Wilkins, PhD, RD, senior extension
associate at the division of nutritional sciences at Cornell
University, pointed out in her “Food Citizen” column
in the Albany Times Union on October 1, 2006, that the outbreak
was amplified because the contaminated spinach from one or a
few farms was mixed with spinach from numerous other farms,
then bagged by a few processors, marketed under several brands,
and distributed nationally and internationally.8 This sort of
centralized food system has more opportunities for contamination
that can reach many people, while a smaller, local food system
is easier to trace and does not offer such widespread consequences.
“One big problem is the traceability of
foods. When people buy their food in a grocery store, they don’t
know how it got there. We do not know the history of the food
and we have lost our connection to the land,” says Harmon.
“I see this as an encouragement to localize.”
Regulations Down on
the Farm
Experts feared the big one was coming. There had been 19 outbreaks
of food-borne illness caused by E. coli O157:H7 in lettuce or
leafy greens. The FDA had written a letter to the lettuce industry
in November 2005 warning about the ongoing risk for product
contamination. The FDA developed the Lettuce Safety Initiative
in response to recurring outbreaks of E. coli O157:H7 in lettuce
with the goal of reducing public health risk by focusing on
the product, agents, and areas of greatest concern. In August
2006, the California Department of Health Services, the USDA,
and the FDA met with industry and academia to further clarify
the goals and plan the Lettuce Safety Initiative. Then all hell
broke loose.
What sort of regulations are in place for produce
growers? Farmers need to comply with FDA, Environmental Protection
Agency, USDA, Occupational Safety & Health Administration,
U.S. Department of Labor, and state and local regulations. The
FDA also developed the voluntary Guide to Minimize Microbial
Food Safety Hazards for Fresh Fruits and Vegetables in 1998,
which offers the industry guidance on Good Agricultural Practices
(GAPs). The guide covers agricultural water, wild and domestic
animals, worker health and hygiene, the production environment,
postharvest water quality, and sanitation of faculties and equipment.
“The current food safety program components or tools such
as GAP, HACCP, and GMPs [Good Manufacturing Practices] are sound
and effective at reducing risk of food-borne illness. But clearly
everyone in the industry must know about these tools and understand
how to use them effectively,” says David Gombas, PhD,
vice president of scientific and technical affairs at United
Fresh Produce Association.
In reaction to the spinach outbreak, the FDA
and the State of California now expect the industry to develop
a plan that will minimize the risk of another outbreak, but
the implementation of the plan will be voluntary. One big problem
some complain about is the word voluntary, which shows up in
guidelines to the industry.
Marion Nestle, PhD, MPH, reported in an editorial
posted on October 23, 2006, in The Mercury News that the food
safety system needs an overhaul, noting that Congress has not
given the FDA the authority or resources to enforce safety procedures
on farms.9
Building Farm Firewalls
for Food Safety
Some produce growers and processors are taking charge of food
safety. “The industry is evaluating and enhancing best
practices, evaluating and recommending means of compliance,
and, together with the government, academia, and industry experts,
developing a long-term research agenda. We now must focus on
ensuring industrywide compliance of current and future best
practices,” says Gombas.
Natural Selection Foods and Earthbound Farm
set in place an unprecedented food safety program on September
28, 2006, that includes rigorous testing and analysis of field
operations from the seed to harvest. They report that the seed,
irrigation water, soil, soil amendments, plant tissues, and
wildlife will be tested, monitored, and certified. The sanitation
protocols for farm equipment, packaging supplies, and transportation
vehicles will be enhanced and monitored. And they have installed
a “firewall,” which means that every lot of freshly
harvested greens brought to their facility will be tested before
entering their processing stream. This program is modeled after
the program the beef industry successfully implemented.
Earthbound Farm reported that they will have
heightened protocols fully implemented in all growing fields
by spring 2007, such as certifying that seeds are free of pathogens
prior to planting; certifying that soil amendments such as compost
and fertilizers are free of contaminants before they are used;
testing and monitoring water sources for harmful bacteria; regularly
monitoring environmental conditions in the field; making frequent,
unannounced inspections of growers’ fields and equipment;
training field harvesters on quality standards and sanitation;
and refrigerating salad greens within the hour they’re
harvested and maintaining an unbroken cold chain.
Benbrook says, “I take my hat off to Natural
Selection Foods. These are unprecedented preventative food safety
measures.”
Western Growers, an agriculture trade association
whose members grow, pack, and ship 90% of the fresh fruits,
nuts, and vegetables grown in California and 75% in Arizona
(roughly one half of the nation’s fresh produce), also
announced that it would take action to initiate a California
Marketing Agreement and a Marketing Order that would establish
mandatory GAPs to strengthen spinach and leafy green food safety
practices.
Education on the Farm-Food
Safety Connection
The FDA and growers have pointed out that consumers need to
be educated that fresh perishable produce and precut or peeled
produce need to be stored in a clean refrigerator at temperatures
of 40° F or below. The FDA, in conjunction with the Produce
Marketing Association and the Partnership for Food Safety Education,
has developed a national produce handling education campaign
to help better educate consumers on handling produce.
“Dietitians need to know about food safety.
We have to be spokespeople. We want people to have faith in
the food supply,” says Krakowski, who reports that something
as simple as educating people to rinse fruits and vegetables
and use vegetable brushes on produce before they are consumed
is important. “Food safety is part of the dietary guidelines.
It should be included when dietitians talk to their clients.”
“I think some dietitians have a hard time
seeing how agriculture relates, but it’s all related to
health,” says Harmon, who notes that educating the public
about food safety is an important part of the field. “The
first message is to keep food safe in the kitchen, and then
there’s keeping it safe in the big picture, which involves
a discussion about knowing how food is grown and how it is produced.
We have a big job to do.”
— Sharon Palmer, RD, is a contributing
editor at Today’s Dietitian and a freelance food and nutrition
writer in southern California.
References
1. Smith DeWaal C, Barlow K, Hicks G. Outbreak Alert! Closing
the Gaps in Our Federal Food-Safety Net. 2005. Washington, D.C.
Center for Science in the Public Interest. Available at: http://www.cspinet.org/new/pdf/outbreakalert2005.pdf
2. NBC11 Exclusive: Preventing Spinach E. coli
Outbreak, Survey: Will you Eat Spinach Again? Available at:
http://www.nbc11.com/news/10234732/detail.html
3. FoodNet. Preliminary FoodNet Data on the
Incidence of Infection with Pathogens Transmitted Commonly Through
Food — 10 States, United States, 2005. MMWR. 2006;55(14):392-395.
4. Rangel JM, Sparling PH, Crowe C, et al. Epidemiology
of Escherichia coli o157:H7 outbreaks, United States, 1982-2002.
Emerg Infect Dis. 2005;11(4):603-609.
5. Cho S, Bender JB, Diez-Gonzalez F, et al.
Prevalence of shiga toxin-encoding bacteria and shiga toxin-producing
Escherichia coli isolates from dairy farms and county fairs.
Vet Microbiol. 2006;118(3-4):289-298.
6. Valcour JE, Michel P, McEwen S, et al. Associations
between indicators of livestock farming intensity and incidence
of human Shiga toxin-producing Escherichia coli infection. Emerg
Infect Dis. 2002;8(3):252-257.
7. Schroeder CM, Zhao C, DebRoy C, et al. Antimicrobial
resistance of Escherichia coli o157 isolated from humans, cattle,
swine, and food. Appl Environ Microbiol. 2002;68(2):576-581.
8. Wilkins J. Food safety should be a priority.
Albany Times Union. October 1, 2006. Available
here.
9. Nestle M. The Spinach fallout: Restoring
trust in California produce. The Mercury News. October 23, 2006.
Available here.
Safe Produce Resource
Guide
Centers for Disease Control and Prevention, http://www.cdc.gov
FDA, Center for Food Safety and Applied Nutrition,
http://www.cfsan.fda.gov
Gateway to Government Food Safety Information,
http://www.foodsafety.gov
International Food Information Council, http://www.ific.org
National Restaurant Association Educational
Foundation, http://www.nraef.org
Partnership for Food Safety Education, http://www.fightbac.org
USDA Food Safety Information Center, http://foodsafety.nal.usda.gov
Onions, Lettuce, E.
coli … Oh My!
Hold the onions, er, lettuce, please? In the most recent food
contamination incident to date, as many as 71 people in the
Northeast were sickened with E. coli bacteria late last November
with a link to Taco Bell. Taco Bell leaned toward green onions
(which are sprinkled on many of their food items) as the contaminated
food source, but after investigation, the Centers for Disease
Control and Prevention named lettuce as the likely source, although
cheddar cheese and ground beef were also considered.
Five states, primarily New Jersey, New York,
and Pennsylvania, were affected by the outbreak, as health officials
and restaurant owners struggled to find the culprit food source
to maintain food safety for customers. More than 90 of Taco
Bell’s 5,800 nationwide restaurants closed for several
days during the scare, and all stopped using green onions altogether—the
first suspected E. coli source. As an extra precautionary measure,
Taco Bell, owned by Yum! Brands, Inc., changed its Northeastern
produce supplier.
In an unrelated incident late last November,
approximately 50 people sustained symptoms related to E. coli
poisoning and several were hospitalized after eating at another
taco chain, Taco John’s, in the Midwest.
— Juliann Payonk is an editorial assistant
at Today’s Dietitian.
