Posting Date: February 8, 2010
Ferreting Out the Truth about Food Safety
I'll bet you remember this one from your childhood: "Don't cross your eyes, they could get stuck that way." And how about this one: "If all your friends were going jump off a bridge, does that mean you'd have to jump off one, too?"
A lot of those are total nonsense — if you've ever crossed your eyes, you realized that they didn't get "stuck that way" (although my friend Steve the cartoonist once drew a cartoon along those lines that leaves me in stitches to this day). But perhaps the silliest of all is, "What you don't know can't hurt you."
We've all figured out by now that what we don't know about the safety of our food supply can most definitely hurt us. Did the person who tossed my favorite salad at the restaurant wash his hands after returning from the restroom? Was the peel of that lemon washed before that slice was plunked into my glass of water? To what temperature was my burger cooked? These are questions I'd definitely like to have answers for, and I'm sure you would, too.
To estimate the number of brown stomach worms in a pasture, researchers place a worm-free calf on grass for a measured length of time, then check for parasite eggs in its feces. (Photo by Keith Weller)
* Imagine a vaccine — no, make that two vaccines — against the dreaded Escherichia coli O157:H7. Actually, you don't have to imagine them, because they're a reality! But this isn't a vaccine for us humans; it's for cattle.
"Wait a minute," I can hear you saying, "E. coli doesn't even make cattle sick." Yes, that's true; this particularly horrendous bacteria can thrive in cattle's intestines without causing them to ever show a sign of illness. But in humans, E. coli can cause repercussions ranging from diarrhea to a life-threatening condition called hemolytic uremic syndrome that can shut down your kidneys.
If we can stop E. coli from proliferating inside the cow, that could help limit contamination of meat at packing houses, and can also reduce shedding of the bacteria in the animal's manure. That manure-borne E. coli can hitch a ride in runoff water and slide right into our drinking water supplies, or it can end up in irrigation water, contaminating fruits, vegetables and other crops.
One of the new vaccines is made up of cells of a strain of E. coli O157:H7 that is lacking a gene called hha, while the second one lacks both hha and a second gene called sepB. Either vaccine causes the body to produce a lot of what are known as immunogenic proteins. These proteins actually trigger the immune system response that prevents E. coli O157:H7 from being able to colonize the cattle's intestines.
In tests with Holstein calves immunized with either form of the vaccine, then given a dose of E. coli O157:H7, the ones that received either of the vaccines had reduced or non-detectable levels of E. coli in their manure within just a few days after being challenged with the bacteria.
* Here's a family you don't want to invite into your house: Enterobacteriaceae. That's a bacterial family that includes all sorts of nasty characters, including the human pathogens Salmonella and Shigella. Unfortunately, Enterobacteriaceae are known to contaminate the shell-egg processing environment.
To pin down where these bacteria might be lurking, and how many different species there might be, ARS scientists in Georgia did an unusual kind of "survey." They took swab samples — at two egg processing plants during three visits apiece — of the plywood-shelved carts that are used to transport into the plant eggs from hens housed in buildings not connected to that plant.
Their findings: 100 percent prevalence for Enterobacteriaceae on the carts at one plant, and 80 percent at the other. There was not only Escherichia, but also Enterobacter, Klebsiella and Salmonella, among others.
But this is actually good news, because once plants know which bacteria are present and where they're lurking, they can develop strategies for reducing and removing these bacterial contaminants.
Like the old saying goes, "Knowledge is power!"
The Agricultural Research Service is the chief in-house scientific
research agency of the U.S. Department of Agriculture. You can read
more about ARS discoveries at http://www.ars.usda.gov/news/.
About the author
"Everybody's
Science" is written by Sandy Miller Hays, Director of Information for
the Agricultural Research Service, the chief scientific research agency
of the U.S. Department of Agriculture. Hays is a native of Fort Smith,
Ark. From the late 1970s until early 1988, Hays was a reporter, editor
and columnist at the Arkansas Democrat (now the Arkansas Democrat-Gazette),
a Little Rock-based daily newspaper. She joined the ARS Information
Staff in 1988, and became Director of Information in April 1998.