Federal health officials say a network they set up last year to identify deadly "nightmare bacteria" is helping control these germs, but the system would be more effective if more hospitals and doctors participated.

A new study from the Centers for Disease Control and Prevention focuses on particularly odious germs that live primarily in the gut and cannot be killed with "antibiotics of last resort," called carbapenems.

CDC Deputy Director Dr. Anne Schuchat calls them "nightmare bacteria" because "they are virtually untreatable." As many as half of patients with these infections die, she says.

These bacteria are known as "enterobacteriaceae," and can include E. coli, Klebsiella, and Enterobacter. They can cause urinary tract infections and sepsis. They normally respond to antibiotics unless they have taken up a trait that causes drug resistance.

The CDC identified more than 1,400 people who tested positive for these kinds of germs last year, including 221 who harbored newer, rare variants that have not yet spread across the country. They are most often found in people who have spent time in nursing homes and hospitals.

One form of resistance, known as KPC, has already spread widely throughout the U.S. since it was first isolated in North Carolina back in 2001. But the CDC is trying to prevent four other strains, which have cropped up in isolated pockets, from taking hold.

As part of that effort, in January 2017 the CDC established a nationwide network of labs to make it easier and faster to identify these killer bacteria. The CDC now reports that the first nine months of that effort were successful, though they turned up more of these rare germs than Schuchat expected.

"These rare resistance patterns were widespread," she tells NPR. "Basically no age, race or gender was spared."

But detecting these rare germs also presents an opportunity. Once a case is detected, the CDC, along with state and local health officials, can swoop in and reduce the chance that these germs will spread. Infection control measures in nursing homes and hospitals can be ramped up. Medical personnel and family members who have been in close contact with these patients can be tested rapidly to see if they are also carrying the dangerous bacteria.

"Because of the additional testing capacity that we have, we have found a lot of these scary bacteria around the country but we've found them in ones and twos and not everywhere," Schuchat says. "So there's a chance to keep them from becoming widespread."

That effort appears to be working. The percentage of bacteria carrying these potentially deadly drug-resistance features is on the decline, according to the CDC's new "Vital Signs" report in Morbidity and Mortality Weekly Report.

The CDC is publicizing these efforts in order to encourage more doctors and hospitals to send their samples along to state testing labs or one of the seven labs that the CDC has established to run these samples quickly.

And, despite gains in the United States, the problem is growing rapidly worse elsewhere in the world. The use – and misuse – of antibiotics is increasing quickly, especially in countries without the latest medical care.

"We have to be doing this not only in the U.S. but across the world because this problem is definitely worldwide," says Dr. Jason Newland, a pediatrician at Washington University in St. Louis and a spokesman for the Infectious Diseases Society of America.

Indeed, at least some of the cases the CDC identified were among people who had surgery overseas and got ill once they returned home.

Copyright 2018 NPR. To see more, visit http://www.npr.org/.