<prompt> Most common organism involved in nosocomial infection -Staph aureusE. coliLegionellaStrep pneumonia  <response>: UTI is the most common type of nosocomial infection. . Most common cause of UTI --- E coli . Most common cause of UTI in ICU --- Candida . Overall staph aureus is a leading cause of nosocomial infection. . Staph aureus is the most common cause of surgical wound infection - . Most common cause of primary bacteremia -- Coagulase negative staphylococcus. REF : ananthanarayana 10th ed 