title: Antibiotics in agriculture and the risk to human health: how worried should we be?
abstract: The use of antibiotics in agriculture is routinely described as a major contributor to the clinical problem of resistant disease in human medicine. While a link is plausible, there are no data conclusively showing the magnitude of the threat emerging from agriculture. Here, we define the potential mechanisms by which agricultural antibiotic use could lead to human disease and use case studies to critically assess the potential risk from each. The three mechanisms considered are as follows 1: direct infection with resistant bacteria from an animal source, 2: breaches in the species barrier followed by sustained transmission in humans of resistant strains arising in livestock, and 3: transfer of resistance genes from agriculture into human pathogens. Of these, mechanism 1 is the most readily estimated, while significant is small in comparison with the overall burden of resistant disease. Several cases of mechanism 2 are known, and we discuss the likely livestock origins of resistant clones of Staphylococcus aureus and Enterococcus faecium, but while it is easy to show relatedness the direction of transmission is hard to assess in robust fashion. More difficult yet to study is the contribution of mechanism 3, which may be the most important of all.
authors: Department of Epidemiology, Harvard School of Public Health Boston, MA, USA.
authors: Qiuzhi
authors: Q
authors: Chang
authors: Department of Epidemiology, Harvard School of Public Health Boston, MA, USA.
authors: Weike
authors: W
authors: Wang
authors: Infectious Disease Unit, Sheba Medical Center Ramat-Gan, Israel ; The Sackler School of Medicine, Tel-Aviv University Tel-Aviv, Israel.
authors: Gili
authors: G
authors: Regev-Yochay
authors: Department of Epidemiology, Harvard School of Public Health Boston, MA, USA.
authors: Marc
authors: M
authors: Lipsitch
authors: Department of Epidemiology, Harvard School of Public Health Boston, MA, USA.
authors: William P
authors: WP
authors: Hanage
keywords: Enterococcus; Staphylococcus aureus; agriculture; antibiotic resistance; food; resistance transfer