Bacterial Cytological Profiling of a Novel Polymyxin Analog, SPR741, that Allows Penetration of Antibiotics into Gram-Negative Bacteria Posted on June 24, 2019 at 3:17 pm.Written by Spero Therapeutics View Presentation Post navigation Next-generation Polymyxin Analog SPR206 – Oral PresentationThe Impact of Varied Test Conditions on the In Vitro Activity of SPR206, a Next-Generation Polymyxin B Analog, against Drug-susceptible and Multidrug-resistant Gram-negative Pathogens