Promising hospital anti-infection strategy probably won't work, s...( Hospital patients increasingly face ten...)

But a new model shows that the practice of cycling alternating between two or more classes of antibiotics as often as every few months probably will not work. It is an unexpected finding at a time when clinical tests of the practice with real patients are in progress.

"We were really surprised. We expected to find a number of cases where it would work, and it was the exact opposite," said Carl Bergstrom, a University of Washington assistant professor of biology.

Instead of cycling, Bergstrom said, hospitals could probably help patients more by prescribing a variety of antibiotics, a method known as mixing. That means instead of having a standard, rotating antibiotic that is used routinely within a single unit, such as intensive care, or even throughout the hospital, a more effective strategy would be to have two or more generally prescribed antibiotics being administered randomly. Two people sharing a room could routinely receive different antibiotics.

Bergstrom noted that antibiotic mixing already is relatively common, not as a conscious strategy but rather because individual doctors develop preferences for the types of medications they prescribe. That can instigate the same type of antibiotic variety as mixing would introduce.

The theory behind antibiotic cycling is that, just as a pathogen strain begins to adapt to a particular antibiotic, a new antibiotic is introduced and the pathogen must start from scratch in building resistance. However, the model implies that pathogens actually encounter new antibiotics more frequently when hospitals use antibiotic mixing than when they use cycling, so cycling is unlikely to reduce res
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Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
9-Aug-2004