Antibiotics are losing their effectiveness around the world as bacterial pathogens become resistant to some drugs. But by how much and over what time?
In order to communicate the average effectiveness of the set of antibiotics used to treat a given bacterial infection, researchers set out to develop a drug resistance index (DRI) that could be understood by non-practitioners, including policy-makers.
For exposition purposes, they constructed DRIs for two pathogens, Escherichia coli and Acinetobacter spp. using U.S. data from 1999 through 2006. They calculated a static-use DRI, which assumes antibiotic use remains fixed to the baseline year, and an adaptive-use DRI, which reflects the ability of physicians to substitute more effective drugs as they become available.
The static DRI for E. coli rose from 0.25 to 0.30 over the time studied. However, the adaptive DRI rose less, from 0.25 to 0.27, indicating that prescribing patterns mitigated the burden of antibiotic resistance.
For Acinetobacter spp., however, there was no difference between the static and adaptive DRIs. Both rose from 0.41 to 0.48, signaling that physicians were unable to adapt to resistance and that there were limited treatment options.
Such trends in resistance are important when setting national treatment guidelines, essential drug lists or hospital formularies.