MRSA Evolves As It Moves Between Humans and Livestock

Feb 21, 2012

Researchers connected with Northern Arizona University have discovered the origins of a strain of anti-biotic resistant staph.

Their new study appeared this week in the on-line journal mbio, published by the American Society of Microbiology..

The bacterium started in humans, moved to animals, then moved back to humans again.

And in the course of its journey, it developed its resistance to antibiotics.

First some basic terms.

Staphylococcus aureus, or staph, is a common bacterium.

It likes warm wet places like our noses and throats.

About 30 % of us carry it.

And it can move between us as innocently as a through a hand shake.

If the bacterium gets out of hand, or travels where it shouldn’t, like our blood stream, we get staph infections….and that can kills us.

Hospitals treat hundreds of thousands of staph infections each year.

Over the past 50 years, modern science has come to the rescue with antibiotics.

One of them is methicillin.

But staph is a very adaptable little bug, and one of its relatives is something called MRSA.

That stands for Methicillin Resistant Staphylococcus Aureus.

In other words, the anti-biotic doesn’t work on it.

If you get MRSA, you’ve got a serious medical problem.

"MRSA kills 18,000 Americans every year.  It kills more people than HIV," said Lance Price.

Price teaches at Northern Arizona University, and he does research at the Translational Genomics Research Institute, or TGen.

He recently joined up with 20 researchers worldwide to study a strain of what’s called pig MRSA.

It seems humans aren’t the only ones to get staph infections.

"If you go to the CDC’s website and read about MRSA you’ll learn about the 5 Cs of MRSA transmission," he said.  " It’s crowding,  skin to skin contact, compromised skin, contaminated surfaces, and lack of cleanliness."

And Price argues there are few places where the five Cs are more prevalent than a concentrated animal feed lot.

"You have pigs or chickens," said Price, "or whatever species crowded together, in totally unsanitary conditions, surfaces covered with feces, and then you introduce the magic ingredient, which is antibiotics and that’s just an invitation for drug resistant bacteria."

In fact pig MRSA is not rare among people who work with livestock in these situations.

And Price’s researcher looked at pig MRSA DNA, and they were able to trace it to a non MRSA strain of human staph.

So in other words, humans passed the staph to the pigs, the pigs developed MRSA, and then the humans contracted the pig MRSA.

It doesn’t strain the intellect to imagine such a contagious little bug bouncing across species.

What’s relevant says Price is that medicine is trying to do something about human MRSA.

He said, "Physicians are being told not to throw antibiotics at every sniffly kid, and parents are learning they shouldn’t demand antibiotics every time their kid has a head cold, so there’s all these programs to get this antibiotic use in human medicine under control."

But, says Price, farmers and livestock breeders are still using millions of pounds of "antibiotics to make animals grow faster, to compensate for overcrowding, for unsanitary conditions and then sometimes for therapy, but most of the antibiotics are being used for production purposes."

Price feels something has to be done to close the circle.

Because even if doctors are trying to limit the use of antibiotics,  the livestock industry isn’t.

And since we know MRSA can jump species, he worries we’re headed toward a cliff where none of our antibiotics work anymore.

"We’ve run out of antibiotics," said Price.  "We’re not discovering them, and we’re definitely not discovering them at the same pace that the bacteria are becoming resistant to antibiotics and so that cliffs edge is not getting any long and we’re barreling toward it at the same speed and we’re about to fall off."

At this time, says Price, Pig MRSA’s not a threat to those of us who don’t live around or work with livestock

And he still eats meat.

He just recommends we follow the same advice we’ve been taught for years about cooking with meat. 

Cook it well and clean your hands, utensils, cutting boards and counters well after contact.