The Center for Disease Dynamics, Economics & Policy

Scientists have been aware of antibiotic resistance since shortly after the discovery of penicillin, western medicine’s first antibiotic.  To a certain extent resistance is inevitable—as we use an antibiotic over time, resistance to the drug gradually evolves, making infections more difficult to treat and necessitating new and more powerful drugs.  However, the development of resistance is also impacted by our actions—for example by how often we prescribe and use antibiotics, and how well we control and prevent infections acquired in the hospital.

Extending the Cure’s ResistanceMap tracks changes in resistance levels across regions of the United States from 2000-2009, covering common bacteria-drug combinations.  The maps tell a story of growing resistance to commonly used antibiotics and identify regional differences in resistance levels.

Data and Methodology

These series of maps explore the spatial distribution of regional resistance levels for common combinations of antimicrobials and organisms. Sets include methicillin-resistant S. aureus, ciprofloxacin-resistant E. coli, penicillin-resistant S. pneumonia and other clinically relevant pathogens found in the hospital and community environments. The maps cover the 2000-2009 period and are organized by the nine US census divisions within the continental United States. For a list of states in each census sub-region, please see www.census.gov/geo/www/us_regdiv.pdf.

The information used to make the maps is provided by The Surveillance Network Database - USA (TSN).  At the core of the data are individual bacterial isolates tested for resistance to certain antimicrobial agents. Isolates are collected electronically from participating clinical microbiology laboratories. Each laboratory reports on isolates gathered from one or more hospitals. The participating institutions are nationally representative and come from more than 150 zip codes across the country. The number of hospital beds represented by the data is set to roughly match the hospital beds in each state.

The numbers used to make the maps are stratified by isolate source into inpatient and outpatient samples, where inpatient includes ICU and nursing home admissions. State-level data is aggregated at the regional level. For each drug-bug combination, regional resistance rates are calculated as the ratio of strictly resistant isolates to the total number of collected isolates in a given region. Every video includes a trend line graph depicting the evolution of resistance rates at the national level year by year. Given below it is the total sample size (N) used to make each map for a given year.

A limitation of the data is that laboratories may join or leave the database over time. Generally, no more than 10% of the sample will change over the course of a year. However, the number of participating sites may vary annually, especially for the last two years of the period. As a result, in some of the maps, certain states are not represented in all years. The aggregation by region is necessary to overcome this problem and cover the entire country. This method relies on the assumption that states within a region share similar resistance rates because of their geographic proximity.

About Extending the Cure

Extending the Cure is a research and consultative effort that frames the growing problem of antibiotic resistance as a challenge in managing a shared societal resource.  It is funded in part by the Robert Wood Johnson Foundation through its Pioneer Portfolio, which supports innovative projects that may lead to breakthrough improvements in health and health care.   It is a project of the Center for Disease Dynamics, Economics & Policy.

Interested in Partnering with ResistanceMap?

To add a ResistanceMap button or banner to your website, contact resistancemap@cddep.org.