Background Antibiotic resistance is a growing problem worldwide, but communicating this challenge to policymakers and non-experts is complicated by the multiplicity of bacterial pathogens and the distinct classes of antibiotics used to treat them. It is difficult, even for experts aware of the pharmacodynamics of antibiotics, to infer the seriousness of resistance without information on how commonly the antibiotic is being used and whether alternative antibiotics are available. Difficulty in aggregating resistance to multiple drugs to assess trends poses a further challenge to quantifying and communicating changes in resistance over time and across locations.
Methods We developed a method for aggregating bacterial resistance to multiple antibiotics, creating an index comparable to the composite economic indices that measure consumer prices and stock market values. The resulting drug resistance index (DRI) and various subindices show antibiotic resistance and consumption trends in the USA but can be applied at any geographical level.
Findings The DRI based on use patterns in 1999 for Escherichia coli rose from 0.25 (95% CI 0.23 to 0.26) to 0.30 (95% CI 0.29 to 0.32) between 1999 and 2006. However, the adaptive DRI, which includes treatment of baseline resistant strains with alternative agents, climbed from 0.25 to 0.27 (95% CI 0.25 to 0.28) during that period. In contrast, both the static-use and the adaptive DRIs for Acinetobacter spp. rose from 0.41 (95% CI 0.4 to 0.42) to 0.48 (95% CI 0.46 to 0.49) between 1999 and 2006.
Interpretation Divergence between the static-use and the adaptive-use DRIs for E coli reflects the ability of physicians to adapt to increasing resistance. However, antibiotic use patterns did not change much in response to growing resistance to Acinetobacter spp. because physicians were unable to adapt; new drugs for Acinetobacter spp. are therefore needed. Composite indices that aggregate resistance to various drugs can be useful for assessing changes in drug resistance across time and space.
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To cite: Laxminarayan R, Klugman KP. Communicating trends in resistance using a drug resistance index. BMJ Open 2011;1:e000135. doi:10.1136/bmjopen-2011-000135
Funding Research time for RL was supported by the Global Antibiotic Resistance Partnership under a grant from the Bill & Melinda Gates Foundation and by the Extending the Cure project under a grant from the Robert Wood Johnson Foundation's Pioneer Portfolio.
Competing interests None.
Patient consent Consent was not obtained as the data are anonymised and risk of identification is low.
Contributors RL initiated and coordinated the research. RL wrote the manuscript with assistance from KK. Both authors saw and approved the final version.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Statistical code is available from the corresponding author at . No additional data are available.
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