GRAND-ABC is designed as a prospective parallel matched cohort, which will run for a year in each of the eight participating hospitals. The primary cohort is a random sample of all Gram-negative infections occurring in a participating hospital during the study period. This cohort can be divided on the basis of the primary determinant status (whether the Gram-negative pathogen is resistant or not based on Dutch guideline for multi-drug resistant organisms; Werkgroep Infectiepreventie (WIP). Bijzonder resistente micro-organismen (BRMO). December 2012. http://www.wip.nl/free_content/Richtlijnen/130424_BRMO.pdf) into two parallel subcohorts. Each patient in each of the subcohorts will be matched to one patient without a gram-negative infection. Together these will form the secondary cohort of non-infected patients: patients admitted to the hospital during the study period who are within the same risk set as the infected patients.