Purpose of review:  Combination therapy is a common strategy for treatment of  multidrug resistant infections. Despite the strong twin rationales of  improving efficacy and reducing resistance development, the evidence  supporting this strategy remains controversial. The aims of this review  are to assess the most recent studies supporting the use of combination  therapy for treating infections because of carbapenem-resistant  Enterobacteriaceae (CRE) and to highlight relevant areas for further  research.

Recent findings:  Evidence supporting the use of combination therapy for the  treatment of CRE remains limited to in-vitro experiments and  observational studies with considerable risk of bias. Very few  antibiotic combinations have been tested in well designed randomized  controlled trials, making it difficult to draw general conclusions for  clinical practice.

Summary: Further studies are urgently needed to test the most promising  synergistic combinations. New drugs potentially active against CRE  should also to be tested in studies with adequate sample size and truly  representative of the general patient population.