May 19, 2021
By Erica Kaufman West, MD
Over the last decade, researchers have shown that shorter courses of antibiotics for multiple different infections have proven effective, including for intra-abdominal infections, gram-negative bacteremias, and others. For those wanting to delve deeper, a website created by Dr. Brad Spellberg outlines many of the studies that support shorter courses. However, Staphylococcus aureus has always been put on the pedestal that still requires 14-plus days of antibiotics. Until now.
Researchers in Denmark conducted a retrospective cohort study, recently published in Clinical Infectious Diseases, to evaluate a shorter course of therapy for patients with uncomplicated infections as defined by IDSA criteria. They included adults with methicillin-sensitive Staphylococcus aureus (MSSA)–positive blood cultures who received <16 days of antibiotics, as those with longer courses most likely had a complicated infection (osteomyelitis, endocarditis). Notably, they excluded patients who had positive blood cultures >48 hours into therapy. Short-course (SC) therapy was 6 to 10 days and prolonged-course (PC) therapy was 11 to 16 days. The primary outcome was death within 90 days, and a secondary outcome was 90-day relapse.
A total of 1,005 patients (291 SC and 714 PC) were included. There was no statistical difference in 90-day mortality or 90-day relapse. The SC group averaged 8 to 9 days of therapy and the PC group 13 to 14 days; importantly, the median treatment course in the SC group was 50% of the PC. The overall mortality rate ranged from 17% to 23%, a sobering reminder of how deadly this infection can be. The relapse risk was 7% overall. This study, while retrospective, gives promising results that uncomplicated MSSA bacteremias can safely be treated with a week of therapy rather than the 2 weeks we’ve all been taught was necessary.