KNAU and Arizona News
10:01 am
Mon April 18, 2011

Flagstaff study finds "superbugs" in meat products

Flagstaff, AZ – Lance Price grabs a package of chicken in a Flagstaff grocery store. He holds it up, and points out the red juices collected at the bottom.

"You see that liquid that sometimes ends up in your grocery bag? It's almost definitely contaminated with drug resistant bacteria "

Dr. Price is the director of the Center for Food Microbiology and Environmental Health at TGen in Flagstaff, and the study's lead author. Researchers at TGEN tested meat and poultry products from 80 different brands in five cities across the U.S., including Flagstaff. What they found surprised him.

"Nearly half the samples were contaminated with staph, and nearly half the staph from the samples were multi drug resistant, resistant to three or more antibiotics."

So if someone were to get infected with that strain of staph, a doctor would have a lot fewer options to treat it.

Price's study does not link the staph-tainted meat and poultry directly to human disease. But it does link the staph back to the farms where the meat is produced often with widespread use of antibiotics.

Price opens the door to the main lab at TGEN. He points out a DNA sequencer.

On a computer screen Price points out what's called an electropherogram, basically a pattern of colored peaks.

"Each of these colored peaks is a different base of DNA, so it's the sequence that allow us to assign a sequence type to each of the staph isolates that we found in the food."

This high-tech genomic sequencing showed that different strains of staph were contaminating different kinds of meat products. Price says that's evidence that the animal is the predominant source of the staph bacteria.

"If this was just contamination with human staph at slaughter or at retail, you'd expect a more homogenous pattern, you'd expect all the different meat groups to be contaminated with the same kind of staph."

Scott Hurd at Iowa State University says, "I think that's a reasonable enough argument IF they tested enough samples and if they had also tested the animals."

Hurd is the former Deputy Undersecretary of Food Safety at the USDA.

"The most important thing to understand about this study is this is not a national prevalence estimate, they only took 136 samples, it's important that you not extend those findings beyond what they really are."

Hurd says staph is everywhere on our skin, in our noses, and that a portion of that staph is probably going to be resistant. Still, he says that studies like this one have prompted farmers to re-examine how they administer antibiotics.

"So it's not like we're saying there's no problem let's go on our merry way, but I don't think the level of risk we've been able to measure with quantitative risk assessment, the level of risk does not require the kind of draconian responses that some countries in northern Europe have implemented."

Like banning the use of antibiotics except when an animal is sick, something the EU has done. But there are lots of researchers in the U.S. who also advocate that approach. Stuart Levy is an epidemiologist at Tufts University and author of "The Antibiotic Paradox."

"I always feel a little embarrassment as I travel when I have to say that we still in this country use antibiotics for growth promotion."

Levy points to new figures showing that 80 percent of all antibiotics in this country are given to farm animals; only 13% to humans. He says we can't ignore that in light of the huge threat posed by antibiotic resistant pathogens.

"We face now on a daily basis patients with infections that are resistant to all but on or a few antibiotics, this is new, this is mounting, and its more and more of a problem. And we want to know how to stop it!"

Levy says the drug-resistant bacteria developing on farms don't stay put. They infect farm workers, and now we know they can hitchhike into grocery stores. Lance Price says the next step is to see if it's actually causing infections in people.

"That's the big question that comes out of our research here. Wow, there's a lot of staph in the food supply, there's a lot of strains that we know can infect people, but can they infect people from meat."

That's a tough question to answer. We've been using antibiotics in food production and in medicine for 60 years. So there's a lot of bleed-over between the two.