July 18, 2012

High Winter Sales of Antibiotics Affect Resistance Patterns

Washington, D.C.—Patterns of drug resistance are affected by seasonal changes in outpatient antibiotic use, according to a new study that used data from U.S. retail pharmacies from 1999 to 2007.

The study, published in Clinical Infectious Diseases, shows the effects of the boost in retail sales of antibiotics in the winter and cautions that hospital campaigns to reduce inappropriate antibiotic use may be ineffective unless they are coordinated with efforts in the community.

Research by Ramanan Laxminarayan, PhD, director of the Center for Disease Dynamics, Economics and Policy in Washington, D.C., and colleagues shows a link between changing rates of antibiotic consumption and resistance.

"Considering that approximately 260 million antibiotic prescriptions are filled each year," the authors write, "individual hospitals' efforts to restrict antibiotic usage are unlikely to have a large effect on certain pathogens unless complemented by and coordinated with campaigns at the community level."

The study used test results from more than 300 laboratories around the U.S. In nearly all cases analyzed, a 1-month lag was found between high antibiotic prescription sales and the prevalence of resistant E coli and S aureus.

According to the study, prevalence of resistant E coli was significantly correlated with lagged (by 1 month) antibiotic prescriptions for aminopenicillins (0.22, P = .03) and fluoroquinolones (0.24, P = .02), which are highly prescribed, but was uncorrelated to antibiotic classes with lower prescription levels. Fluoroquinolone prescriptions were also significantly correlated with a 1-month lag with the prevalence of ciprofloxacin-resistant MRSA (0.23, P = .03).

One way pharmacists can help lower unnecessary antibiotic use, according to the authors, is by continuing to promote immunization against influenza.

Noting that the U.S. still uses more antibiotics per capita than most comparable countries, Laxminarayan said, “decreasing inappropriate use through flu vaccinations and better education of both patients and physicians on when to use antibiotics will have an immediate impact."

In future studies, the researchers plan to examine other combinations of antibiotics and resistant bacteria, and to focus on subpopulations in the U.S.

U.S. Pharmacist Social Connect