- Study 1 The sample size for the CRE and CRAB cohorts were calculated so that the cohorts may serve as 'historical' cohorts for future comparison with new drugs for CRE and CRAB. To do so, and because the estimates for the outcome variable of the new drug is unknown, we seek to estimate the clinical cure rate of BAT with 95% confidence interval and 8% precision. For an estimated cure rate of 50% based on data from previous studies, 151 patients for each of the five types of infection are needed (due to CRE: cUTI, pneumonia, cIAI, and BSI; due to CRAB: BSI). However, because around 25% of patients will not receive BAT, we will need 201 patients per type of infection except for BSI due to A. baumannii, for which we will need 221 because some blood isolates identified as Acinetobacter spp in sites not specifying the species will not be A. baumannii (total, 1025 patients). Such sample size will be enough also to investigate the best available therapy with the merged CRE cohorts.