A report by Uranga, et al. of a randomized trial of 312  patients with pneumonia  published recently in JAMA Internal Medicine,  has found that continuing  antibiotics more than 5 days gives no additional benefit if the patient is stable and has been afebrile for 48 hours.  Neither the word “evolution” nor the phrase “natural selection” appear in the article.

An accompanying commentary by Spellberg puts the study in context and makes the connection with evolutionary biology. Among other conclusions it states,”There is no evidence that taking antibiotics beyond the point at which a patient’s symptoms are resolved reduces antibiotic resistance. To the contrary, specifically for pneumonia, studies have shown that longer courses of therapy result in more emergence of antibiotic resistance,6,7 which is consistent with everything we know about natural selection, the driver of antibiotic resistance.” 

The beginning of that commentary is below.
” In ad 321, Roman Emperor Constantine the Great codified that there would be 7 days in a week. Even in the modern era of evidence-based-medicine, this 1695-year-old decree remains a primary reference for duration of antibiotic therapy: it leads physicians to treat infections in intervals of 7 days. Thus, it is gratifying when clinical trials challenge the standard antibiotic duration of 7 to 14 days.”

“In the past, community-acquired pneumonia was treated with a 7- to 14-day course of antibiotics. However, clinical trials in the early 2000s demonstrated that 3 or 5 days of protocol-specified antibiotics are as efficacious as longer courses of therapy for patients with mild to moderately severe community-acquired pneumonia.1,2 To this body of literature is now added a new randomized trial, in this issue of JAMA Internal Medicine, by Uranga et al,3 comparing short-course vs longer courses of therapy for hospitalized patients with community-acquired pneumonia. The trial used a pragmatic design in that treating physicians were allowed to select their preferred antibiotic for the first 5 days of therapy. Patients were randomized such that on day 5 those in the control group continued the therapy selected by their treating physicians and those in the experimental group had their antibiotics stopped if they were afebrile for 48 hours and had no more than 1 sign of clinical instability (eg, hypotension, tachycardia, tachypnea, or hypoxia). These criteria for stopping the antibiotic applied to 70.1% of patients in the experimental arm. Although patients admitted to the intensive care unit were excluded from the trial, a substantial number (approximately 40%) of patients in both arms had Pneumonia Severity Index scores of IV to V, indicative of severe illness. In contrast, prior studies of short-course antibiotic therapy have focused primarily on patients with mild to moderate illness”…(read more-not open access)

Uranga, A., España, P. P., Bilbao, A., Quintana, J. M., Arriaga, I., Intxausti, M., … Capelastegui, A. (2016). Duration of Antibiotic Treatment in Community-Acquired Pneumonia: A Multicenter Randomized Clinical Trial. JAMA Internal Medicine. http://doi.org/10.1001/jamainternmed.2016.3633 (not open access)

Spellberg, B. (2016). The New Antibiotic Mantra—“Shorter Is Better.” JAMA Internal Medicine. http://doi.org/10.1001/jamainternmed.2016.3646