The time course of bacterial killing was studied by exposing overnight grown cultures of MRSA (ATCC BAA-1556) and E. coli (ATCC BAA-2452) to lead cyclic peptides (15c and 16c) at their MIC and 4×MIC in MHB media as described previously. Aliquots (50 μL) were drawn at a fixed time interval and plated after dilution (up to 10 8 ) and plated onto on MH agar plates. Viable colonies (CFU) were counted after 24 h incubation at 37 °C. Untreated bacterial culture was used as a control. The bactericidal kinetics of the standard antibiotics daptomycin, polymyxin B, and ciprofloxacin were also determined at their respective MIC and 4×MIC concentrations.