There was yet more discussion of this topic on the foodsafe list. More
information about food safety and the archives of this list can be found
at http://www.nal.usda.gov/fnic/foodborne/foodborn.htm
This message is relatively long. At the end is a message on a different
topic: ORGANIC VEGETABLE SOUP ASSOCIATED WITH A CASE OF BOTULISM
I will forward three other messages to illustrate the food safety slant
to the grass-fed beef story.
Andy
To: Andy Clark <aclark@nal.usda.gov>
Subject: FSnet Sept. 10/98 (fwd)
---------- Forwarded message ----------
Date: Thu, 10 Sep 1998 23:17:14 -0400
From: Douglas A Powell <dpowell@uoguelph.ca>
To: FSNET-L@LISTSERV.UOGUELPH.CA
Subject: FSnet Sept. 10/98
FSNET SEPTEMBER 10, 1998
<snip>
**********
FSnet is produced by researchers at the Agri-Food Risk Management and
Communications Project at the University of Guelph, is edited by Douglas
Powell (dpowell@uoguelph.ca) and Amanda Whitfield (awhitfie@uoguelph.ca),
and is supported by the Ontario Ministry of Agriculture, Food and Rural
Affairs, Health Canada, the Australian Meat Research Corp., the U.S.
National Food Processors Association, the U.S. National Pork Producers,
AGCare (Agricultural Groups Concerned About Resources and the
Environment), Monsanto Canada, Hedley Technologies Inc., Ag-West Biotech
Inc., Qualicon, L.L.C., DeKalb Canada Inc., Pioneer Hi-Bred Limited
(Canada), the U.S. National Cattlemen's Beef Association, Canadian Animal
Health Institute, Novartis Crop Protection Canada, Maple Leaf
Meats/Poultry, Caravelle Foods, CKE Restaurants Inc., the Rutgers
University Food Safety Extension Program, the Ontario Soybean Growers
Marketing Board, the Canadian Cattlemen's Association, Food Industry
Environmental Network and the Agricultural Adaptation Council (CanAdapt
Program).
archived at:
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**********
CATTLE DIETS COULD CONTROL E. COLI DANGER; SIMPLE CHANGE IN CATTLE DIETS
COULD CUT "E. COLI" INFECTION, USDA AND CORNELL SCIENTISTS REPORT
Sept. 10/98
Cornell University News Service press release
ITHACA, N.Y. -- A simple change in cattle diets in the days before
slaughter may reduce the risk of "Escherichia coli" ("E. coli") infections
in humans, U.S. Department of Agriculture (USDA) and Cornell University
microbiologists have discovered.
Research reported in the Sept. 11 issue of the journal "Science" indicates
that grain-based cattle diets promote the growth of "E. coli" that can
survive the acidity of the human stomach and cause intestinal illness. "E.
coli" contamination is responsible for more than 20,000 infections and 200
deaths each year in the United States.
Fortunately there is a workable solution to the food-safety problem, the
scientists say. By feeding hay to cattle for about five days before
slaughter, the number of acid-resistant "E. coli" can be dramatically
reduced.
"Most bacteria are killed by the acid of stomach juice, but "E. coli "from
grain-fed cattle are resistant to strong acids," explains James B.
Russell, a USDA microbiologist and faculty member of the Cornell Section
of Microbiology. "When people eat foods contaminated with acid-resistant
"E. coli"including pathogenic strains like O157:H7 -- the chance of
getting sick increases."
"E. coli "is a normal bacterium in the gastrointestinal tract of animals
and humans, and most types are not harmful (See ""E. coli" and Cattle"
fact sheet, attached). However, disease-causing strains such as "E. coli"
O157:H7 produce toxins that cause bloody diarrhea or even kidney failure
in humans. Mature cattle are unaffected by "E. coli" O157:H7. Only a small
number of cattle (estimated at 1 to 2 percent at any one time) shed "E.
coli" O157:H7 in their feces, a rate that is not fully explained.
When beef carcasses are accidentally contaminated by feces at slaughter,
the pathogens can enter the human food supply. "E. coli" O157:H7 can be
killed by cooking or irradiation, but the bacterium continues to pose a
food-safety risk.
Cattle are fed starch-containing grains to increase growth rate and
produce tender meat. Because the bovine gastrointestinal tract digests
starch poorly, Russell explains, some undigested grain reaches the colon,
where it is fermented. When the grain fermentsand acetic, propionic and
butyric acids accumulate in the animal's colona large fraction of "E.
coli" produced are the acid-resistant type.
"Grain does not specifically promote the growth of "E. coli" O157:H7, but
it increases the chance that at least some "E. coli " could pass through
the gastric stomach of humans," Russell says. "The carbohydrates of hay
are not so easily fermented, and hay does not promote either the growth or
acid resistance of "E. coli". When we switched cattle from grain-based
diets to hay for only five days, acid-resistant "E. coli" could no longer
be detected."
In studies performed at Cornell, beef cattle fed grain-based rations
typical of commercial feedlots had 1 million acid-resistant "E. coli", per
gram of feces, and dairy cattle fed only 60 percent grain also had high
numbers of acid-resistant bacteria. In each case, the high counts could be
explained by grain fermentation in the intestines.
By comparison, cattle fed hay or grass had only acid-sensitive "E. coli",
and these bacteria were destroyed by an "acid shock" that mimicked the
human stomach, the microbiologists report in "Science".
According to microbiologist Russell, acid-resistant strains of bacteria
have evolved to overcome the protective barrier of the gastric stomach.
The ongoing process of natural selection allows organisms with the
appropriate genes to survive and multiply where others cannot. Because
cattle have been fed high-grain, growth-promoting diets for more than 40
years, he says, there has been ample opportunity to select acid-resistant
forms.
Further research is needed to identify the acid-resistance genes of "E.
coli", but Russell says that "common laboratory strains" of "E. coli"
appear to lack the necessary DNA to survive acidic gastrointestinal
environments.
"In the meantime, now that we know where the acid-resistant "E. coli" are
coming from, we can control them with a relatively inexpensive change in
diet," Russell says. "This strategy has the potential to control the
production of other acid-resistant bacteria, including virulent strains of
"E. coli "that have not yet evolved."
A brief period of hay-feeding immediately before slaughter "should not
affect either carcass size or meat quality," and the diet change could be
implemented with minimal expense and inconvenience to feedlot operators,
according to Donald H. Beermann, Cornell professor of animal science.
USDA microbiologist Russell has been stationed in Ithaca for more than 17
years and is affiliated with the U.S. Dairy Forage Research Center in
Madison, Wisc. He holds the rank of adjunct professor of microbiology at
Cornell, and the other authors of the "Science" report were his students
when the feeding studies were conducted: Francisco Diez-Gonsalez,
currently a postdoctoral fellow, completed his Ph.D. in animal science at
Cornell in 1996. Todd Callaway is a Ph.D. candidate in microbiology. Menas
Kizoulis, a Cornell senior in biological sciences, was recently awarded a
Howard Hughes Undergraduate Fellowship to continue research in Russell's
laboratory.
The studies were supported by the Agricultural Research Service of the
USDA.
EDITORS: A photo of the researchers is available at
http://www.news.cornell.edu/releases/Sept98/acid.relief.hrs.html
"E. coli" and Cattle Facts
Source: U.S. Food and Drug Administration Center for Food Safety
and Applied Nutrition, USDA Agricultural Research Service, Cornell
University Section of Microbiology
TRILLIONS AND TRILLIONS: The gastrointestinal tract of animals and man is
an ideal habitat for the growth of bacteria, and cell densities can be as
high as a trillion cells per gram of digesta. Most gut bacteria are
harmless types, and they can even provide essential nutrients to the host.
When animals consume contaminated food, the native bacteria compete with
the invaders and provide at least some protection against food-borne
illness. "Escherichia coli "is a common bacterium in the GI tract, but it
is usually outnumbered by other types. "E. coli" is never a beneficial
bacterium, but under normal circumstances the animal and "E. coli"
tolerate each other. Some strains of "E. coli", however, are not
people-friendly, and these highly virulent forms can cause acute illness
or even death.
THE GOOD, THE BAD AND THE ENTEROHEMORRHAGIC: "E. coli" is a normal
inhabitant of the human gastrointestinal tract, but strains identified as
O157:H7 are enterohemorrhagic and cause intestinal bleeding. Victims may
experience severe cramping and abdominal pain, watery or bloody diarrhea,
vomiting or low-grade fever for an average of eight days. " E. coli
"O157:H7 also produces "shiga-like" toxins that can cause kidney failure;
once the infection reaches the uremic phase, the death rate can be as high
as 30 percent. As few as 10 viable "E. coli "O157:H7 can cause infection.
THE FECAL CONNECTION: Mature cattle are unaffected by "E. coli" O157:H7,
and a small percentage of the cattle in the United States are carriers.
When meat is contaminated with cattle feces at slaughter or fruit and
vegetables are fertilized with manure, "E. coli" O157:H7 can enter the
human food supply. In day-care facilities and nursing homes, fecal
contamination is the vehicle for person-to-person infection. Recent work
indicates that swimming pools and water parks can be contaminated with "E.
coli "O157:H7.
RAW DANGER: Heat, in the pasteurization of milk and fruit juices or the
cooking of solid foods, will destroy "E. coli" bacteria. "E. coli" on the
outer surfaces of a steak or chop are easily destroyed by heat of cooking.
But "E. coli" in ground meat may be concealed deep within the hamburger.
Hamburgers having any "pink meat" can still have live "E. coli "O157:H7
cells.
GASTRIC BARRIER: Humans have a natural barrier that kills food-borne
bacteriathe acidic, gastric juices of the stomachbut "E. coli" bacteria
can withstand "acid shock" if they have grown in the presence of
fermentation acids. Fermentation acids increase when cattle are fed large
amounts of grain. Cattle fed grain have very large numbers of
acid-resistant "E. coli". The "E. coli" of hay-fed cattle are
acid-sensitive and are easily killed by gastric juice.
ACID RELIEF: Research indicates that cattle fed hay have 1 million-fold
fewer acid-resistant "E. coli "than cattle fed grain. However it may be
possible to process grains to decrease acid production and acid
resistance. When grains are heat-treated or steam-flaked, less starch
passes to the colon, and fermentation acids decline.
CATTLE DIET LINKED TO BACTERIAL GROWTH
Sept. 11/98
Science Vol. 281, No. 5383, p 1578
Jennifer Couzin
In a related news story in Science to accompany the above paper, Gary
Schoolnik, chief of the infectious disease division at Stanford University
Medical School, was quoted as saying, "This [research] is in a class by
itself. [It] opens the door to a whole field of research that needs to be
done."
Schoolnik suggests deliberately infecting cows with the O157 strain, so
that researchers can directly compare its incidence in animals fed hay and
grain diets rather than focusing broadly on the bacteria as Russell's team
did. More work will also be needed to test a practical implication of the
new finding: that switching cattle to hay a few days before they are
slaughtered could limit the frequency of dangerous E. coli outbreaks.
The story goes on to say that not all microbiologists were convinced by
the data in the paper, however.
Michael Doyle, who directs the Center for Food Safety and Quality
Enhancement at the University of Georgia, Griffin, was cited as arguing
that lauryl sulfate broth, used to determine the numbers of E. coli by
dilution, is no more selective for E. coli than other bacteria and would
not reveal an
accurate count, adding, "The methods as they're written" don't make sense.
Author Russell was cited as countering that although lauryl sulfate isn't
a foolproof selection method for E. coli, "the results were confirmed by
other tests." For example, the researchers showed that, as expected for E.
coli, the
bacteria could grow in a medium containing lactose, releasing carbon
dioxide gas as an end product.
Fred Owens, a ruminant researcher at Optimum Quality
Grains in Des Moines, Iowa was quoted as saying, "I think
people in feed lots are going to be hesitant to institute a change" in
cattle diet, citing logistical problems, such as having to transport and
store large quantities of hay, as well as a potential drop in market value
should the cows' weight fall while on hay.
John La Montagne, deputy director of the National Institute of Allergy and
Infectious Diseases was quoted as saying, "I think whatever steps we think
make sense we ought to consider doing. E. coli O157 is a big problem,
potentially a very big problem."
SAFER BEEF
Sept. 10/98
AP
By LAURAN NEERGAARD
WASHINGTON -- The first wire story out about the new story says that
scientists have discovered a simple way to dramatically reduce the risk of
people getting sick from E. coli-tainted beef: Change what cattle eat for
a few days before they're slaughtered.
The story quoted USDA microbiologist James Russell, who did the study
while stationed at Cornell, as saying, "It's a way of attacking the
problem long before the animal reaches the slaughterhouse, the meat
reaches the supermarket or the meat is prepared by the consumer. We're
very
hopeful" the result will be far fewer sick Americans.
Robert Buchanan of the Food and Drug Administration, lead scientist for
the Clinton administration's food safety initiative, was quoted as saying,
"This looks to be a relatively inexpensive, potentially important
intervention that farmers can do." And it would save farmers money. "Hay
is a lot cheaper than oats," Buchanan noted.
Gary Cowman, quality assurance chief for the National Cattlemen's Beef
Association was quoted as saying, "We think it's a major breakthrough.
It's something very, very practical."
But there are still questions to be answered, he cautioned,
including whether abruptly changing a cow's diet from starchy grain
to fibrous hay overnight would cause digestive problems. Cowman
said more research should settle those concerns within a year.
ORGANIC VEGETABLE SOUP ASSOCIATED WITH A CASE OF BOTULISM -- NORTHERN
ITALY
September 10, 1998
Eurosurveillance Weekly
A case of botulism in northern Italy arose following consumption of a
vegetable soup, which was contaminated with Clostridium botulinum. The
patient, a woman of 58 years who lives in the province of Verona (Veneto
region), drank the soup (ribollita, which forms part of Tuscanys regional
cuisine) for lunch on 25 August 1998. Six hours later she developed
failure of accommodation, followed by vomiting, dizziness, facial
paralysis, and respiratory distress. The next morning she was admitted to
the local hospital with suspected botulism. Stool specimens analysed at
the National Reference Laboratory at the Istituto Superiore di Sanit (ISS)
contained spores of C. botulinum A.
Local health staff performed a field investigation. Food samples found in
the case's home were taken and analysed, including an open jar of
ribollita. No one else had eaten the same food as the patient in the two
days before she became ill. The cases daughter reported that she had
bought the jar of ribollita and kept it at home at room temperature. The
jar had been opened one week before being used. It was noted to have a bad
smell, but the patient kept it refrigerated after opening until 25 August,
when she drank it. Toxin and spores of C. botulinum A were identified at
ISS in samples of the remaining soup.
The soup had been produced by a small local factory in the province of
Livorno in Tuscany by using organic (grown without use of chemicals)
vegetables (potatoes, green leafy vegetables, courgettes, beans, tomatoes,
onions, celery, parsley), water, olive oil, and salt. The soup was packed
in glass jars with net weights of 340g, 640g, or 920g and sterilised in a
small autoclave at 121C for 35 minutes whatever the size. No quality
control measures were taken: the functioning of the autoclave was neither
verified nor documented.
Additional samples of the same soup and other products from the same
factory are being tested for botulism. All the foods produced have been
withdrawn from the Italian market and an international warning has been
released for products that may have been exported. The incident
illustrates a hazard associated with small scale manufacture of home-made
style foods (1). These are often made with organic ingredients, which are
believed to be healthier and erroneously presumed to require less
stringent heat treatment or quality control.
Reference:
1.Brusin S, Salmaso S. Botulism associated with home-preserved
mushrooms. Eurosurveillance Weekly 1998; 2: 980430.
Reported by Paolo Aureli and Giovanna Franciosa, National Reference
Laboratory for Botulism, and Stefania Salmaso (salmaso@iss.it), Infectious
Disease Unit, Istituto Superiore di Sanit, Rome, Italy.
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