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Antibiotic Resistance Data

By Quinn Eastman

drugs

A new Drug Resistance Index combines a "basket" of resistance data for different drugs, like the way groceries and other household items make up the cost-of-living index.

These numbers are weighted according to the amount of each that is used. If a microbe develops resistance to a drug that has little use, then the index will go up only slightly. If resistance occurs against a drug prescribed to almost every patient, the index will increase more.

"What lab monitoring picks up doesn't map exactly to clinical treatment failures. Resistance to a particular antibiotic matters less when doctors have other choices, and more when they don't," says Keith Klugman, William F. Foege Chair of Global Health, who developed the index with Ramanan Laxminarayan, director of the Center for Disease Dynamics, Economics & Policy.

The idea is to have one number for every microbe in every country. This approach could emphasize the importance of smart drug policies and make it easier to compare resistance in different states or countries.

In studying antibiotic resistance patterns in the United States, the researchers found considerable diversity in antibiotic use across the country. "There's more variation, both regionally and locally, than we had initially expected," Klugman says, but the five states with the highest antibiotic use are all in the Southeast: West Virginia, Kentucky, Tennessee, Louisiana, and Alabama.

The researchers also found that over the past decade, antibiotic use overall has fallen by about 12%. However, prescription rates for a class of antibiotics called fluoroquinolones (an example: ciprofloxacin) have increased by 49% from 1999 to 2007, while resistance is increasing. These drugs are now much less likely to work against E. coli, the most frequent cause of bacterial infections.

With the CDC, Klugman is examining patterns of use and resistance data for a bacterium that is a major cause of childhood ear infections.

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