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Defensive measures against a super bug

Times Staff Writer

It’s a paradox of modern medicine: High-tech marvels such as heart surgery and kidney transplants are helping people live longer, but they’re also providing new targets for a dangerous type of bacteria.

Staphylococcus aureus causes about half a million infections -- sometimes referred to as staph infections -- a year. The infections often occur in people who have had surgery to insert heart valves and stents, catheters, even artificial hip joints. And because S. aureus regularly reinvents itself, it’s now resistant to a wide range of antibiotics. That can be life-threatening for people with serious infections.

At Harbor-UCLA Medical Center’s Research and Education Institute, scientists are at the forefront of research on the bug that may lead, within the next few years, to new ways to arrest it.

Led by Dr. Arnold S. Bayer, one of the world’s leading authorities on S. aureus, the research team is going beyond the traditional use of antibiotics, studying ways to cripple the bacteria before they can seize control in the body. Already, a vaccine is being tested that may protect very ill newborns from deadly staph infections.

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“These organisms are good warriors,” says Bayer, associate program director of the Adult Infectious Disease Division at Harbor-UCLA Medical Center. “They’re armed to the teeth with mechanisms to infect patients at risk. It’s the ultimate pathogen.”

The bacteria love stents and catheters, in particular, because they can grow either on the artificial material or on human tissue. As more people undergo procedures to insert artificial devices, S. aureus has more opportunities to thrive.

“The pool of people at risk is increasing and more antibiotics are being dumped in. But that is driving [antibiotic] resistance,” Bayer says.

The goal is to find solutions that don’t rely on antibiotics to kill the bug, says Michael R. Yeaman, also a member of the institute’s infectious diseases team.

“Using an antibiotic to sterilize the landscape of a tissue is one approach. But only one approach,” Yeaman says. “We’re interested in ways that won’t pressure the organism into developing resistance. It’s how do we not have a war here?”

To avoid doing battle with S. aureus, the team is using new knowledge about the genetic structure of the bacterium to find ways to cripple it. Bayer, for example, is working on a vaccine that could remove the bug’s ability to adhere to surfaces. A clinical trial testing the vaccine is underway on low birth-weight babies, who also are susceptible to the infection.

The vaccine project is in collaboration with a Georgia-based biotechnology company, Inhibitex Inc.

Other researchers at the institute are exploring whether the body’s defense systems can be harnessed to better attack an infection, Yeaman says. Most people, he notes, are assaulted by a variety of filthy bugs each day and don’t fall ill.

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“Something is really working well” in those cases, he says. “The question is, how do we make our own immune system work more effectively?”

Scientists also are taking a close look at the molecules in aspirin because S. aureus seems to be affected by chemicals similar to aspirin. “In 10 years we’ll be treating staph infections in a multidimensional way,” Bayer says. “It won’t be with one drug.”

And that’s good news. About 70% of all deaths are due to an infection, Yeaman says. “Unless we can defend ourselves,” he says, “we will succumb to infection.”

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(BEGIN TEXT OF INFOBOX)

The staph file

* Between 30% and 50% of people carry the Staphylococcus aureus bacteria. The bacteria usually reside in the nose.

* Staph can enter the body through a cut in the skin. In serious infections, the bug then spreads to adjacent tissue, nearby organs or through the blood stream, causing such dangerous illnesses as pneumonia, blood poisoning or even the “flesh-eating” necrotizing fasciitis. Highly aggressive treatments are needed to stop the infection.

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* Staph infections (caused by S. aureus and another type called S. epidermis) are diagnosed in about 500,000 people a year in the United States.

* Hospitalized patients with surgical wounds are particularly vulnerable to staph infection. Hospital staph infections cause between 60,000 and 80,000 deaths each year.

* About 95% of staph bacteria are resistant to penicillin and about 30% are resistant to synthetic penicillin antibiotics.


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