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C. diff: The next
O157? Source of Article: http://www.meatpoultry.com/Feature_stories.asp?ArticleID=99975
Making definitive statements about Clostridium difficile’s
evident residency in meat products and livestock is risky at best. Some of
the research concerning "C. diff," as it is often called, is
worrisome, even frightening; other research much less so. And scientists
themselves are quick to point out that at this point what’s not known about a
meat connection with C.diff far outweighs what is
known. "Just because C.diff is showing up in food
may not mean it’s a problem in food. And as far as C.diff
in livestock is concerned, we really don’t know much about the human-animal
connection with C.diff. That picture isn’t clear at
all," comments Dr. Liz Wagstrom, assistant
vice president for science and technology at the National Pork Producers
Council. Nonetheless, C.diff in pork and hogs
"is something we’ve been following for a long time," she adds. Dr. Brandi Limbago, the lead researcher for
bacterial characterization, typing and identification in the Centers for
Disease Control and Prevention’s Clinical and Environmental Microbiology
Branch, is only a bit more definite. "We know a fair amount about
Clostridium difficile in the health-care
environment, and we know it has been found on meat and in livestock, but
there are a lot of dots and pieces between these facts that are still
blank," she says, noting that studies have found similar strains of C.diff – "some of them indistinguishable from each
other" – in humans and food animals. But the microbiologist, who has
worked and published with Dr. Glenn Songer at the
Univ. of Arizona, one of the world’s leading C.diff
researchers, quickly adds: "While it’s very interesting that Clostridium
difficile has been found in meat, there’s no
evidence that it’s foodborne. To the best of our
knowledge, it’s not a foodborne disease." Songer himself is less sanguine. C.diff, he says, "could be the next O157 – or it
could be nothing. I suspect it’ll turn out to be something in between."
He adds: "People in the industry really want to know if this is really a
problem or not. I understand that. But we have to think it is before we can
think it isn’t." A menace and a killer The pathogen is a well-known menace in health-care facilities, especially
in nursing homes and convalescent hospitals with large populations of older,
immune-compromised patients. C.diff infection
brings on diarrhea and can lead to dangerous inflammations of the colon – colonitis – if not caught and checked early. Health
authorities say it probably causes thousands of deaths, and perhaps tens of
thousands of deaths, in health- care facilities every year. (Canadian
authorities blame C. diff for roughly 2,000 deaths over 2003 and 2004 in a
single province, The usual treatment for pathogenic infection, a regimen of antibiotic
therapy, is nearly useless against C.difficile,
because antibiotics clear out resident microflora
and leave behind, in the human gut, a kind of microbiological desert, which C.diff appears to be especially well-equipped for
exploiting. According to a study released last November by the Association
for Professionals in Infection Control and Epidemiology, 13 out of every
1,000 hospital patients becomes infected by C.diff,
a rate up to 20 times greater than had previously been estimated. Just as
worrying, a virulent new strain, NAP1, has emerged, and its toxin is 20 times
more potent than other strains. Moreover, NAP1 has proven to be resistant to fluoroquinolone antibiotics such as Cipro
and Levaquin. It’s a proven killer: A pregnant
mother of twins spontaneously aborted and then died from C.diff
infection, according to a 2005 CDC review. It is the virulent new strain,
however, that has been found on meat and in livestock. "It’s a very difficult pathogen to get under control," says Dr.
David Theno, the recently retired director of
technical services at Jack in the Box and one of the industry’s leaders in
the battle against E. coli O157:H7. "You’ve got to be really aggressive
with it. As the population ages, we’re going to have to figure out a way to
effectively deal with it, no question." According to the Mayo Clinic, "In hospitals and nursing homes, C.difficile spreads mainly on the hands of caregivers,
but also on cart handles, bedrails, bedside tables, toilets, sinks,
stethoscopes, thermometers – even telephones and remote controls." A taste for sausage So what’s it doing in meat? That’s what CDC would like to know. In the
effort to come up with an answer, the federal agency called a meeting, in
mid-December, of C.diff’s leading researchers and
other interested microbiologists and food scientists. The specific purpose of
the meeting, according to Dr. Limbago, who
attended, "was to discuss methods of detection of Clostridium difficile in foods," but the real driver behind the
gathering is the compelling, troubling data gathered by Songer
in Arizona, Dr. Scott Weese at the Univ. of Guelph
in Canada, and Dr. Roger Harvey, a veterinary medical officer with USDA’s
Agricultural Research Service facility in College Station, Texas. Glenn Songer’s studies are, in some ways, the
most worrisome for the meat industry. He found, for the first time, an
identical strain of C.diff in contaminated food and
in hogs. Moreover, the professor of veterinary science also found that more
than 40 percent of packaged-meat samples taken from three He adds that when he first began investigating C.diff
in food a few years ago, "I thought it was a fool’s errand. I couldn’t
believe someone hadn’t found it already. I was sure that if it was there,
someone would have found it. But it seems like no one did look. And when we
finally did, we found it." Weese’s numbers aren’t quite so shocking, but
they remain troubling. His team took C.diff-positive
samples from 18 percent of the ground beef and ground veal tested, though
they did not find the virulent strain, and the numbers of cells the team
found in the positive samples was somewhat lower than what Songer’s team found. "We know we can find it widely in the environment," Weese says. "What we don’t know is how it travels
from farms to food. We’ve got a big gap in our knowledge so far." He points out that C.diff, which was first
identified in 1935 (it was originally named "Bacillus difficile," or "the difficult" microbe),
is unique among pathogens in a couple of ways. One, it can be found among the
gut flora of healthy humans, causing no evident ill effects. This is why, when the population of C.diff cells
suddenly expands (no one knows why), treatment with antibiotics can be so
dangerous; with the other microflora pushed out of
the way by the drugs, C.diff takes over. Another C.diff’s attribute that’s unique: As a spore-forming
microbe rather than a cell-former, it can survive typical cooking
temperatures – think of it as a kind of opposite of Listeria monocytogenes, which survives refrigeration. Still, Weese actually takes some comfort, he
says, in the high rates of positives that Songer
found in the grocery meats. "In some ways, finding it so commonly
downplays the risk. If it’s being found in 40 percent of humans or on 40
percent of meat samples, we know that 40 percent of the human population
isn’t getting sick from it." In search of CCPs As for meat specifically, Weese isn’t ready to
sound alarms. "Meat might be just a carrier, we don’t know. The real
problem might always be spreading from human to human, with meat just an
intermediary. I don’t think the industry should panic at this point – but we
should be concerned." "I can tell you that it’s not coming in to
nursing homes on food," adds Dave Theno.
"It’s already there. In that environment or in a hospital, it can always
move from person to person. We’re talking about a very opportunistic
bug." "We know it can cause illness in baby pigs," says Liz Wagstrom at NPPC. "But C.diff
is not C.diff is not C.diff
– what I mean is, just because it’s in livestock doesn’t automatically mean
meat is a problem. One reason why it may be showing up in ground meats is
because those products are handled by more people than other kinds of meat
products." She also points out that both Weese’s
and Songer’s retail sampling so far has been
regional. C.diff’s national and global distribution
in meat and livestock isn’t yet mapped. "I think it’s something that we
need to look at carefully to see if there’s an emerging problem. But at this
point I don’t believe C.diff is our next BSE or
O157." CDC’s Limbago, who will be discussing C. diff at
a gathering of meat and animal scientists this coming March, emphasizes that
"there’s no epidemiological link" connecting even the
"indistinguishable" strains found in livestock and humans. "Animals
might be just some kind of reservoir," she says, underscoring Weese’s point. In agreement with virtually all other C.difficile researchers and observers, she says it’s just
too early to tell what kind of role meat and livestock play in C.diff’s lifecycle and distribution. Songer is also cautious about sounding alarms,
but he pushes the industry to be proactive. "We can even now probably
get ahead of this," he says. "Let’s find the critical control
points for this, and let’s take care of them." This article can also be found in the digital edition of MEAT&POULTRY,
February 2009, starting on Page 64. Click here
to search that archive. |
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