Drug-resistant staph is proving to be a crisis

Wednesday, October 24, 2007 4:08 PM CDT

By Delthia Ricks
(c) 2007, Newsday

When scientists sounded an alarm last week about the evolving presence of methicillin-resistant Staphylococcus aureus -MRSA -they shed new light on an old problem about a bug that has been evading destruction since the dawn of the antibiotic era.

Their conclusion: MRSA is here to stay. It is an organism that can cause mild skin infections but is capable of invading the bloodstream and causing systemic damage. For years it has been a problem in hospitals, a so-called nosocomial infection. Now it is making its way into communities, infecting people in gyms, schools and day-care centers.

MRSA is a threat because it is drug-resistant -and hardy. But it has plenty of company among microbes -tiny creatures with titanic drug-repelling consequences. Indeed, MRSA got its name, methicillin-resistant Staphylococcus aureus, because it is capable of defeating methicillin, penicillin’s more potent cousin.

“What we have seen is Darwinism in action,” said Dr. Roy Steigbigel of Stony Brook University Medical Center, referring to MRSA’s drug-thwarting capacity as a prime example of survival of the fittest.

The trouble with drug-resistant organisms is frightening: The medical community is running out of drugs to control them.

“This is a major, major health crisis,” said Dr. Michael Pichichero of the University of Rochester, who recently announced the emergence of a new strain of Streptococcus pneumoniae, a master of resistance. This emboldened strain outwits 18 highly complex drugs.

Bacteria, scientists say, become resistant through a variety of mechanisms: Gene swapping between microbes in the environment is one way. Bolder, highly infectious strains exchange genes with milder ones, creating a new superbug in the process. But gene-exchanges can create superbugs even when drug resistance is not an issue. A notorious strain of E. coli is an example. E. coli O157H:7, which has invaded spinach, hamburger, lettuce and other edibles, emerged through a gene exchange.

Twenty-five years ago, virtually all E. coli was harmless. But a bovine form acquired genes from a potentially lethal strain of toxin-producing shigella, and the result has been a food science nightmare. Cows, however, remain immune to the bug.

Some experts say the reason for the emergence of E. coli O157H:7 is unknown; others blame the widespread use of antibiotics in agriculture. Antibiotic overuse kills weak bugs and leaves hardy survivors behind.

Microbes also develop resistance when patients don’t finish a full course of antibiotics. A shortened course destroys weak bugs, but again, hardy ones remain. Antibiotic overuse in hospitals is another reason microbes develop resistance. So much exposure to medications allows them to develop the capacity to resist.

But biological reasons aren’t the only ones behind the increased resistance. Some experts say the pharmaceutical industry’s reluctance to develop new antibiotics leaves doctors with fewer options.

“From a practical standpoint, it makes sense for them to develop drugs that people will take for life, like statins,” said Steigbigel, a professor of medicine, microbiology, pathology and pharmacology. He was referring to drugmakers’ profitable line of cholesterol-lowering drugs. “An antibiotic is a drug that is used for only a short period,” he added. As a result, drug companies earn fewer dollars on antimicrobials.

Dr. Elizabeth Bancroft, an epidemiologist with the Los Angeles County Health Department who recently wrote an editorial in the Journal of American Medical Association calling MRSA’s rise “astounding,” also cites drugmakers’ reluctance to develop new medications as a reason for the rise in resistance.

“The pharmaceutical industry is like any other business,” she said. “These are companies that are profit-driven and, like any profit-driven business, they are going to direct their efforts to the products that make the most money.”

But drug resistance is so formidable that doctors sometimes have to resort to extraordinary measures to treat infected patients.

Pichichero said a pediatric patient of his lost hearing in both ears because S. pneumoniae was resistant to all 18 antibiotics approved for childhood ear infections. When he diagnosed the infection in other children -the most recent case two weeks ago -Pichichero, a professor of pediatrics, immunology and microbiology, had to resort to off-label use of one of the most potent antibiotics on the market: levofloxacin, the stronger relative of ciprofloxacin, which made headlines during the anthrax scare.

“This drug is not approved for children because studies in beagle puppies had shown that it causes cartilage damage,” Pichichero said. He added that he obtained special consent from the children’s parents to prescribe the medication.

Pichichero, however, does not want pharmaceutical companies to develop stronger antibiotics. His hope is for smarter ones that defy the bugs’ capacity to outfox them.

Distributed by the Los Angeles Times-Washington Post News Service