Acinetobacter is less common than other superbugs such as MRSA.
The new bug has doctors worried because they have fewer ways to fight it.
A seven year study from 1999 to 2006 showed samples of Acinetobacter became more antibiotic -resistant over time.
The bug thrives in water so it can live in a patient's lungs, blood or urine and can cause pneumonia or other serious infections.
Experts say the containment of this dangerous microbe needs to become a high priority at American hospitals.
The study appears in the journal "Infection Control and Hospital Epidemiology."