Epidemiological interpretation of studies examining the effect of antibiotic usage on resistance

Abstract

Bacterial resistance to antibiotics is a growing clinical problem and public health threat. Antibiotic use is a known risk factor for the emergence of antibiotic resistance, but demonstrating the causal link between antibiotic use and resistance is challenging. This review describes different study designs for assessing the association between antibiotic use and resistance and discusses strengths and limitations of each. Approaches to measuring antibiotic use and antibiotic resistance are presented. Important methodological issues such as confounding, establishing temporality, and control group selection are examined.

Fig 1

Trends in percent MRSA and incidence of Staphylococcus aureus central line-associated bloodstream infections (CLABSI) in intensive care units, from the National Nosocomial Infections Surveillance System, 1997 to 2004, and National Healthcare Safety Network, 2006 to 2007. MSSA, methicillin-susceptible S. aureus. (Reprinted from reference with permission of the publisher. Copyright © 2009 American Medical Association. All rights reserved.)

Fig 2

Types of quasiexperimental study designs used in antibiotic resistance research (Modified from reference with permission of the Infectious Diseases Society of America.)

Fig 3

Relationship between quinolone consumption (top) and susceptibility of E. coli isolates from urine cultures to quinolones (bottom), by month. The shaded area is the intervention period; to the left is the preintervention period, and to the right is the postintervention period. DDD, defined daily dose. (Modified from reference with permission of the Infectious Diseases Society of America.)

Fig 4

Suggested guidelines for evaluating studies examining the effect of antibiotic usage on resistance.