Clinical efficacy of fosfomycin combinations against a variety of gram-positive cocci

Abstract

IntroductionOver recent years we have witnessed an increase in the resistance of microorganisms to the available antimicrobials and a decrease in the number of new antimicrobials. Fosfomycin is a safe and cheap broad-spectrum antibiotic which has shown very promising results in combination therapy, mainly against gram-negative microorganisms. Little is known, however, about its clinical efficacy against gram-positive microorganisms. MethodsWe performed a retrospective review of all patients with severe gram-positive infections who received fosfomycin as part of their treatment from 2011 to 2017. We also performed in vitro time-kill assays to study the behaviour of fosfomycin with different antimicrobials against two strains of methicillin-resistant Staphylococcus aureus (MRSA) and two strains of methicillin-susceptible S. aureus (MSSA). ResultsSeventy-five patients were treated with different fosfomycin combinations. Among them, 61 (81%) were successfully treated. Daptomycin plus fosfomycin was the most effective combination. Overall, the treatment with fosfomycin was safe, and side effects were minor. There was only one major side effect that resolved after discontinuation of therapy. Time-kill studies demonstrated increased activity of fosfomycin combinations, with daptomycin–fosfomycin being the most active combination against both MRSA and MSSA strains. ConclusionsOur results suggest that antimicrobial combinations including fosfomycin are an alternative and effective approach for gram-positive infections.