Antibiotic Resistance Investigations Indicate Both Good, Bad News

According to UI findings, a novel synthetic drug linezolid was universally active against all tested forms of staphylococci regardless of resistance patterns to other antibiotics. The new drug also inhibited all enterococci and was 100 percent effective against streptococci.

"Linezolid appears to be a very promising new antimicrobial agent," said Ronald Jones, M.D., UI professor of pathology. "We have not found any documented cases where the drug has not been effective."

Jones and Michael Pfaller, M.D., UI professor of pathology and public health, will present their findings at the 37th annual meeting of the Infectious Diseases Society of America to be held Nov. 18-21 in Philadelphia. The UI investigative team is the first, besides the manufacturer Pharmacia & Upjohn, to test the effectiveness of the drug.

"One of the most exciting potential uses for this new agent is the management of resistant Gram-positive infections," Pfaller said.

That potential may be even more important considering the findings that UI colleague Daniel Diekema, M.D., a UI pathology fellow and infectious diseases staff physician, will report at the same meeting.

According to the UI study led by Diekema, Pfaller and Jones, similar and sometimes identical antibiotic-resistant strains of S. aureus are popping up hundreds and thousands of miles apart, even across oceans.

"We demonstrated that there are numerous instances where bacterial strains were present at many different hospitals in the same region and at hospitals on different continents," Diekema explained.

The medical community has been using antibiotics to treat bacterial infections for more than

60 years. However, many bacterial strains have become immune to most of the available drugs meant to destroy the organisms. Much of this immunity, or resistance, is due to overuse of the drugs themselves.

In the study Diekema will present, the UI investigators wanted to find out the genetic relatedness of antibiotic resistant S. aureus strains in various areas of the world. The UI researchers also wanted to identify places where resistance was the highest. To conduct the probe, the UI team relied on the global network of 72 medical centers that participate in the SENTRY Antimicrobial Surveillance Program sponsored by Bristol-Myers Squibb. SENTRY is a joint effort between the UI and the Women's and Children's Hospital, Adelaide, Australia. The program is the first and only worldwide monitoring system for the spread, over time, of bacteria resistant to antibiotics.

"We did this particular study because it is very important to understand how these resistant strains are being spread around the world," Diekema said.

The findings, which showed that many of the resistant strains cross national borders and that the biggest resistance problem areas are located in Central and South America and in Asian-Pacific countries, are important as infectious disease control specialists attempt to combat the resistance, Diekema stressed.

"If resistance emerges within an individual hospital because of antibiotic use, then the best way to control that resistance is to crack down on antibiotic use," he said. "However, if very resistant strains are being spread widely between hospitals, then the best approach is to emphasize infection control practices. In the case of S. aureus, it looks like these resistant strains are very easily spread in hospitals, among hospitals and even across continents. What that means to us is that even though antibiotic control is important for this bacteria, even more important probably are good infection control practices."

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