Between June 1, 2004, and March 14, 2005, 16 patients in the surgical/medical intensive care unit (ICU) at a Chicago hospital were infected and another 2 were colonised with multidrug-resistant (MDR) Acinetobacter baumannii. This study describes the systematic investigation initiated to discover an environmental reservoir and a novel measure taken to terminate the outbreak. Am J Infect Control. 2009 Nov 7. [Epub ahead of print]