An 85-year-old woman with dementia is admitted to hospital with worsening confusion, new urinary incontinence and constipation. These symptoms suggest a urinary tract infection, but the doctor treating her has a dilemma because the symptoms also suggest her dementia may be worsening or she has simple constipation. Sending a sample to a lab for analysis could confirm bacteria in the urine, but getting a result takes days, so the doctor decides to play it safe and prescribe antibiotics.

Scenes like that are repeated every day in hospitals around the world, and they are leading to excessive and often unnecessary antibiotic use....
What we proved is that antibiotic prescribing supports the idea that resources that don’t clearly belong to an individual or a group are likely to be overexploited (known as “the tragedy of the commons”). In fact, healthcare professionals have suspected this for some time, but it had not been rigorously proved until now.

What it implies is that if doctors act in the best interests of their own patients, then prescribing antibiotics whenever a bacterial infection is suspected is always the preferred treatment, irrespective of whether other doctors are doing the same. What makes it a tragedy of the commons is that if all doctors adopt this strategy, then the outcome is worse for themselves and their patients than if they all exercised restraint.