Quantitative human health risk assessments of antimicrobial use in animals and selection of resistance: a review of publicly available reports

Quantitative risk assessments have been conducted to estimate the probability and magnitude of adverse human health effects from antimicrobial use in food animals through selection for antimicrobial resistance in bacteria. The majority focused on licensed antimicrobials under regulatory scrutiny, including growth promoters and agents of critical importance to human health. Most used models to attribute fractions of surveillance-derived estimates of antimicrobial-resistant infections in humans to antimicrobial use in animals. Risk estimates ranged from a few additional illnesses per million at risk, to many thousands. Although useful, published quantitative risk assessments have been unable to comprehensively address important aspects of antimicrobial resistance, including multiple exposure pathways, interrelationships among bacteria, co-selection, and cumulative effects of antimicrobial use in multiple species and countries. However, quantitative risk assessment shows promise for synthesis and analysis of scientific data. Work is required to develop methodology and train more risk analysts. An international forum is needed to pool expertise, review existing risk assessments and disseminate the results to risk managers throughout the world.