He called on doctors, hospital leaders, and health officials to work together to stop the spread of the infections. "Our strongest antibiotics don't work and patients are left with potentially untreatable infections," he said.
Although the bacteria, known as carbapenem-resistant Enterobacteriaceae, or CRE, have not spread to the wider community - as some other germs have - they are more dangerous, said Frieden, who called them a "triple threat."
First, the bacteria are resistant to all or nearly all antibiotics, even those of last resort, he said. Second, they kill up to half of patients who get bloodstream infections from them. And third, the bacteria can transfer their antibiotic resistance to other bacteria in the family, potentially making other bacteria untreatable as well.
For example, one strain, carbapenem-resistant Klebsiella, which caused the NIH outbreak, "can spread the genes that destroy our last antibiotics to other bacteria, such as E. coli, and make E. coli resistant to antibiotics also," Frieden said.
E. coli is the most common cause of urinary-tract infections in healthy people.
In 10 years, the percentage of Enterobacteriaceae resistant to antibiotics rose almost fourfold, to 4.2 percent in 2011 from 1.2 percent in 2001, according to data reported to the CDC. And the strain that caused the NIH outbreak has become seven times more prevalent in the last decade, according to a CDC report issued Tuesday.
During the first half of 2012, almost 200 hospitals and long-term acute-care facilities treated at least one patient infected with these bacteria. The CDC had no figures on deaths.
Enterobacteriaceae are a family of more than 70 bacteria, including E. coli, that normally live in the digestive system. Some have grown resistant to a group of antibiotics known as carbapenems, often called last-resort antibiotics. Over the last decade, CDC tracked one type of CRE from a single health-care facility to facilities in at least 42 states.