A pattern of outpatient antibiotic overuse in parts of the United States -- particularly the Southeast -- could accelerate drug resistance, researchers say.Ramanan Laxminarayan, director of Extending the Cure, and Keith P. Klugman, a professor at Emory University, describe their first-of-its-kind index for tracking resistance.Like a Consumer Price Index for drug resistance, the tool aggregates information about resistance trends and antibiotic use into a single measure of antibiotic resistance over time.In a report, published in the British Medical Journal Open, the researchers said the interactive maps showed antibiotic use in the United States from 1999 to 2007 show how overall antibiotic dispensing has decreased; consumption fell by about 12 percent over this time period.However, their report also showed prescribing rates for a powerful class of antibiotics known as fluoroquinolones shot up by 49 percent from 1999 to 2007 and at the same time, antibiotic resistance is increasing. The drugs are now much less likely to work against E. coli, the most frequent cause of bacterial infections, than they were in 1999.The maps also highlight an alarmingly high antibiotic use across the Southeast compared to states in the Pacific Northwest, Laxminarayan said. For example, residents of West Virginia and Kentucky, where antibiotic use rates are highest, take about twice as many antibiotics per-capita as people living in Oregon and Alaska,The five states with the highest antibiotic use in the nation are West Virginia, Kentucky, Tennessee, Louisiana and Alabama.