 This multi-center, retrospective study of cases of serious bacterial infections including cUTI or AP, HABP, VABP, andor bacteremia caused by CRE will consist of a chart review over a 6 month period from September 1, 2013 to March 1, 2014. De-identified data will be collected from the chart review of at least 150 cases of selected infections due to CRE at approximately 20 sites. 