 In this prospective observational multicenter study we aim to determine the prevalence of oropharyngeal and rectal Gram-negative bacilli colonization in 4 population of hospitalized subjects, and their susceptibility to chlorehexidine. We plan to recruit 300 subjects in surgical wards 100 in orthopedics, 100 in thoracic and vascular, 100 in abdominal surgery and 100 in the ICU. Secondary endpoints are to determine the incidence of the acquisition of such colonization in a 10-day timeframe; determine the phylogentic characteristics of E. coli isolates; to compare the phylogentic characteristics of oropharyngeal and rectal E. coli isolates; to compare the phylogentic characteristics of colonization and potential E. coli infection isolates; to compare the rectal and oropharyngeal colonization composition; description of oropharyngeal microbiote 