Because of the increasing number of XDR-GNB infections locally and worldwide, the questionable efficacy of the current gold standard monotherapy treatment, the paucity of novel and effective antibiotics against such infections for the foreseeable 10-year horizon, and the consistent reports of superiority in in vitro studies, it is critically important that combination therapy should be tested against polymyxin monotherapy in a rigorous clinical trial to ascertain if it represents a more effective treatment strategy. It is also important to determine if the results of multiple combinations bactericidal testing - like more standardized susceptibility testing for single antibiotics - will correlate well with clinical outcomes.