 GSK945237 belongs to the Bacterial Type II Topoisomerase Inhibitor BTI class of antibiotics. GSK945237 has demonstrated in vitro and in vivo activity against Gram positive including methicillin resistant Staphylococcus aureus MRSA and Gram-negative pathogens associated with respiratory tract, skin and soft tissue infections including isolates resistant to existing classes of antimicrobials. This study will be conducted in four 4 parts, with a single oral dose being explored in Part A 2400 mg and repeat oral doses b.i.d. and q.d. being explored in Part B. Parts C and D will be optional evaluations of repeat oral doses of linezolid and a comparative evaluation of the effect of GSK945237 and moxifloxacin, respectively. Parts A and B will be single-blind, randomized, placebo-controlled, dose-rising Part B only studies of healthy subjects to evaluate the safety, tolerability and pharmacokinetics of GSK945237. The proposed doses range from 400 mg to 2400 mg. Part C will be a single-blind, randomized, and placebo-controlled repeat dose evaluation of 600 mg b.i.d. of linezolid. Part D will be a single-blind, randomized, placebo-controlled, two period crossover study. The proposed doses for Part D will be 1200 mg GSK945237 and 400 mg moxifloxacin. 