Resistant bacteria remain public health threat

While new antimicrobial agents are in the pipeline, judicious use of currently available antibiotics continues to be a strong recommendation.

By Susan J. Landers, AMNews staff. May 19, 2003.

Washington -- The threat of severe acute respiratory syndrome has been this year's public health headline grabber, causing fear and panic across the globe.

Still, public health experts point out that other threats continue, for the most part, below the general public's radar screen. And the danger posed by some of these threats, specifically that of antibiotic-resistant bacteria, are viewed as more insidious than many of the spotlight items.

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There have been one or two infectious diseases that have emerged or reemerged every year for at least the past 10 years, noted Neil Fishman, MD, director of the Antimicrobial Management Program at the University of Pennsylvania Medical Center, Philadelphia. He named the hantavirus, the West Nile virus, and mad cow disease as examples. "We've dealt with them," he said. "But antimicrobial resistance has been around for over 60 years, and we really haven't gotten a handle on it yet."

Dr. Fishman was among a panel of infectious disease experts at an April 30 press briefing at the New York Academy of Sciences. The briefing was sponsored by the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America and the Society of Infectious Diseases Pharmacists.

Although the alarm over antibiotic-resistant bacteria has been sounded in the past, recent studies indicate that physicians are still inappropriately prescribing antibiotics, often relying on broad-spectrum antibiotics when there is little clinical rationale for their use.

"We can no longer be complacent about the threat posed by antibiotic-resistant bacteria," said Martin Blaser, MD, chair of the Dept. of Medicine at New York University School of Medicine. "The fact is, we are simply running out of options. We're already seeing infections that fail to respond to the first or even second antibiotic prescribed. If we continue on this course, we're going to find ourselves back in the Dark Ages, when serious infections had no cure."

Of recent concern is the realization that strains of the bacteria Staphylococcus aureus are becoming resistant to vancomycin, an antibiotic often considered to be a drug of last resort. Resistant S. aureus infection has generally occurred in hospitals, but has recently made a jump to the broader community.

"People thought vancomycin was invincible, but bacteria are adaptable organisms that are staying a step ahead of science," said Michael Rybak, PharmD, president of the Society of Infectious Diseases Pharmacists. "What we need are new agents that work differently than what's already out there."

Dr. Rybak said there are some promising new antibiotics and vaccines in the pipeline.

Dead bugs are best

Among the new agents is daptomycin, brand name Cidecin, which has been granted the Food and Drug Administration's priority review status, Dr. Rybak said.

Action on Cidecin could come as early as next month, according to a statement from its developer, Cubist Pharmaceuticals Inc. The drug is a bactericidal agent that is administered intravenously once a day and is intended for complicated skin and soft-tissue infections. The new drug has shown promise in fighting the newly discovered strain of vancomycin-resistant S. aureus.

Antibiotics can either inhibit the growth of bacteria as a bacteriostatic agent or they can kill bacteria as a bactericidal. The latter are favored, Dr. Rybak said, because "dead bugs don't mutate."

Among the other antibiotics on the horizon are oritavancin, a broad-spectrum agent that is also a bactericidal, Dr. Rybak said. Manufactured by InterMune Inc., the drug, now in phase III trials, is being investigated for use in skin and soft tissue infections and for blood infections. Oritavancin has a long half-life, and patients may need only a three- to seven-day course of treatment compared with vancomycin's 10- to 14-day course.

The broad-spectrum antibiotic called dalbavancin is another agent that needs to be injected only once daily. The agent is in phase II trials for catheter-related bloodstream infections and in phase III trials for skin and soft-tissue infections and is manufactured by Vicuron Pharmaceuticals.

And Aventis Pharma's Ketek (telithromycin) is currently awaiting FDA approval for acute episodes of chronic bronchitis, acute sinusitis and community-acquired pneumonia.

There are also a number of vaccines in development, Dr. Rybak reported. For example, StaphVAX, developed by Nabi Biopharmaceuticals, is intended to provide immunity against S. aureus and is now in phase III trials with end-stage renal disease patients on hemodialysis.

But more activity by pharmaceutical firms would help address the continuing problem. "Of the 89 new drugs approved by the Food and Drug Administration in 2002, none were antibacterial agents," Dr. Blaser said.

Pharmaceutical companies don't stand to reap major financial rewards from the development of antibacterial agents.

Although successful broad-spectrum agents hold the potential to make a profit for companies, they are becoming increasingly difficult to develop. While narrow-spectrum vaccines might be easier to develop, they would appeal to only a small market. "If we want to keep ahead of the bacteria, as a matter of public policy we have to find ways to encourage companies to develop what are in essence orphan drugs," Dr. Blaser said.

Physicians also should continue to take steps such as observing good hand hygiene, administering available vaccines to counter influenza and pneumococcal disease and refusing to prescribe antibiotics when they will do no good.

But pressure on office-based physicians continues. It takes about a minute to write a prescription for an antibiotic, but 15 or 20 minutes to explain why an antibiotic won't work for a viral illness, Dr. Fishman said.

He recommends some of the educational resources posted on the Centers for Disease Control and Prevention Web site.

One, a prescription pad for symptomatic care of viral illnesses, has been more useful than might first be apparent, he said. It provides such advice as increasing fluids, using cool-mist vaporizers or saline nose sprays and it gives the patient a sense of confidence that they are leaving the office with something concrete and written that tells them what to do.

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