MRSA in bedbugs and meat--an expert weighs in

MRSA, the potentially deadly bacteria more formally known as methicillin-resistant Staphylococcus aureus, has grabbed quite a few headlines this week.

Canadian researchers found MRSA (and VRE, other drug-resistant bacteria) in bedbugs in Vancouver; and American researchers found MRSA and other staph bacteria on a few samples of supermarket meat in Detroit.

The superbug news comes a month after researchers from a nonprofit biomedical research center found that about half of the grocery store meat they sampled was contaminated with staph bacteria, about half of which were resistant to at least three classes of antibiotics.

To make sense of the MRSA and other drug-resistant bacteria headlines, we talked to food safety researcher Dr. David Wallinga, director of the food and health program at the Institute for Agriculture and Trade Policy in Minneapolis. Wallinga researches, among other topics, how feeding antibiotics to livestock may be contributing to bacterial resistance.

In this edited transcript, based on a phone interview, he explains the risks of MRSA in meat and why the bedbugs don’t worry him as much.

What did you think of the studies that found drug-resistant staph in supermarket meat—from this week and last month?

They raise a bit of an alarm bell on one hand because they’re showing that really, the food supply is a reservoir for resistant staph. We’ve known in the past that the food supply is a reservoir or source for other sorts of resistant bugs that cause food poisoning, such as salmonella, but these sort of studies put a point on the fact that resistant staph now has to be considered a food contaminant as well.

What are specific practices to keep in mind while preparing food?

They’re much as they’ve always been. Make sure the meat is cooked well. Make sure you use good hygiene. What does that mean? Keep your meat away from other raw foods, wash your hands, wash your utensils.

Are there safe levels of bacteria on meat?

I don’t think we’ve got any evidence there’s such a thing as a safe level of superbugs on meat. Having meat that’s not contaminated with superbugs is better than having meat contaminated with superbugs.

How does staph get into your body?

It’s not just one [way], certainly. We’re talking about different kinds of infections.

Staph food poisoning is something you’re ingesting with food. It’s the toxins the staph produces that [cause] symptoms—diarrhea and sickness.

The way MRSA generally makes people extremely sick or kills them is different. It’s when that bug somehow invades the bloodstream and makes you systemically sick.

That could be something that’s already colonized in your body and invades your bloodstream because your immune defenses are down.

One and a half percent of the population is carrying MRSA. Are they all sick? Of course not. But if they go to the hospital for some reason, and their immune system takes a knock, then they’re vulnerable to getting a bad MRSA infection.

In other cases, in prisons and sports teams, people are getting MRSA infections through those wounds or small cuts in the skin.

Hospital-acquired infections have been particularly problematic. How can consumers protect themselves in a hospital setting?

We continue to have very serious problems with resistant infections in hospital settings. I think the best thing is to do whatever you can to not get sick in the first place, and not be a patient in that setting with a depressed immune system. [If you have to be in the hospital, the Centers for Disease Control and Prevention has a few tips to prevent MRSA infections.]

Where do humans carry MRSA?

Mostly in the nostrils. But that’s not the only place you can have it.

What about the new study that found bedbugs as a reservoir?

That’s hugely interesting. They tested five bedbugs. With something so small, you’ve got to take it with a grain of salt. But they found it! And they had an association between people in community with bedbugs and MRSA in hospitals. It certainly bears more study.

That would seem to be the case. Here, an epidemiology professor and blogger offers a similar reaction.

For now, “bears more study” is the key phrase for much MRSA research.

healthkey@tribune.com

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