Is Antimicrobial Resistance a Tragedy of the Commons?

<div><p>(A) Tragedy scenario. A simple model that illustrates the potential for moral dilemma in antimicrobial use. Optimizing antimicrobial use <i>(u)</i> for the good of all requires consideration of both society and the individual patient. (i) Individual health benefit from antimicrobial use <i>I(u)</i>. (ii) Cost to societal health from decreased effectiveness of antimicrobials <i>E(u)</i> as a result of the evolution of antimicrobial-resistant pathogens. We assume that the societal benefit from reducing transmission rates is small and do not include it here. iii) Overall effect of antimicrobial use on societal health <i>S(u) = I(u)E(u)</i>. Ensuring that antimicrobials are only used for infections they can treat is a technical solution that will only take us to the individual optimum, which in this illustrative example is far from the real optimum.</p> <p>(B) Best-case scenario. Low to moderate antimicrobial use has little impact on our ability to treat later infections and is only weakly costly to societal health <i>E(u)</i>. This means there is no tragedy. The true nature of <i>E(u)</i> is unknown but it is a function of investment in both new antimicrobials and infection control, which may be able to shift us from scenario A to scenario B.</p>