DESCRIPTION (provided by investigator): Acinetobacter baumannii has emerged from an organism of questionable pathogenicity to an infectious agent of importance to hospitals worldwide causing increased patient morbidity and mortality. The reasons for the emergence of A. baumannii are unknown and no interventions have been successful at curbing this emergence. For these reasons, A. baumannii is a significant public health problem. To our knowledge, no cohort similar to the one described in this application has been created to investigate the epidemiology of A. baumannii. This knowledge is essential in order to develop and implement new, cost-effective infection control strategies aimed at reducing nosocomial infection and the worldwide spread of A. baumannii. The long-term objective of this renewal application is to continue to understand the epidemiology of emergent Gram- negative bacteria and antibiotic-resistant bacteria with a focus in this application on A. baumannii. The aims of this renewal are: Aim 1) Construct a prospective cohort of intensive care unit (ICU) patients to quantify the proportion of A. baumannii acquisition that is attributable to patient-to-patient transmission. Aim 2) Culture several environmental sites in the hospital rooms of patients colonized and infected with A. baumannii to determine sites of frequent contamination and determine whether terminal cleaning between patients is effective. Aim 3) Identify potential genetic factors that contribute to high transmissibility of A. baumannii using genomic sequencing and comparative genomic techniques. This application is a competitive renewal of an ongoing ICU cohort. The cohort consists of patients admitted to the ICU who have peri-rectal surveillance cultures obtained. The peri-rectal cultures can be used to analyze in a retrospective fashion many bacterial species. The peri-rectal cultures are linked to demographic, comorbidity, laboratory, and medication data that are contained in a relational database. Thus the cohort serves as a rich mechanism of understanding the epidemiology of a number of different emerging bacteria and hospital pathogens.