Acinetobacter is a group of gram-negative, nonmotile bacteria most commonly found in the soil or water. The bacteria have also been found on the skin of healthy people—especially health care providers. Acinetobacter most often colonizes patients in intensive care units (ICUs), particularly those with devices such as endotracheal tubes, indwelling urinary catheters, intravascular catheters, or surgical drains. It can also cause infections. Outbreaks of Acinetobacter infections are typically seen in ICUs and other health care settings that house very sick patients, such as hospice facilities, as well as in nontraditional health care settings, such as nursing homes. Acinetobacter infections have rarely been seen outside these areas. Once the bacteria are introduced in a facility, serial or overlapping outbreaks often occur as a result of various multidrug-resistant strains.

Acinetobacter infections have been clinically prominent in hot, humid areas, such as tropical regions, and are a recurrent problem during times of war and natural disaster. Recently, Acinetobacter infection has been reported in Europe, Asia, and North America, including among U.S. military members injured in the Middle East. There are at least 25 types of Acinetobacter, all of which can cause disease in humans. However, these bacteria cause little risk to healthy people. Those with weakened immune systems, chronic lung disease, or diabetes may be more susceptible to Acinetobacter infection.