Methods: Calculation of the DRI was done as described by Laxminarayan and Klugman (2011). Briefly, the frequency of use of each antibiotic class was multiplied by the aggregated resistance rates of pathogens against which the antibiotic class is used to create a weighted resistance rate. The weighted resistance rates were then summed by each antibiotic class to generate the DRI for each country. Our index included six common bacterial pathogens and the antibiotic classes used for their treatment. The pathogens included were: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecium, and Enterococcus faecalis. The antibiotic classes were: aminoglycosides, broad-spectrum and narrow-spectrum penicillins, carbapenems, cephalosporins, and quinolones. Antibiotic use data were obtained from IMS Health and converted into defined daily doses (DDDs). Antibiotic resistance data were obtained from public and private hospitals, government agencies, and private labs.
Results: DRIs range between 0 and 100, where 0 and 100 represent maximum and minimum antibiotic effectiveness respectively. In 2014, the lowest DRIs were found in Sweden, Denmark and Norway, while India, Greece and Portugal had the highest DRIs. Over the period of our analysis, the highest increases in the DRI were found in developing countries.
Conclusion: The DRI can be a simple, valuable tool to quantify, track and compare antibiotic effectiveness worldwide. The measure would be improved as better quality data on antibiotic use and resistance become available.
S. Gandra, None
R. Laxminarayan, None