The superbug struck the NIH, located just outside Washington.

Washington - A deadly antibiotic-resistant bacteria killed six patients as it spread through the United States government's elite National Institutes of Health (NIH) research hospital last year, US media reported for the first time on Thursday.

The patients died from an outbreak of the bacteria Klebsiella pneumonia, often called a superbug because of its resistance to nearly every available antibiotic, according to the Washington Post.

The superbug struck the NIH, located just outside Washington, when a lung transplant patient was admitted to the hospital in June 2011 without doctors being aware she was infected with the bacteria.

NIH staff isolated the patient once they discovered her illness, but their efforts came too late. It eventually infected 16 others, with the last reported case occurring in January.

The outbreak was not made public until Wednesday, when researchers at the hospital published a paper outlining the methods they used to combat the infection. - Sapa-dpa