A single strain of Escherichia coli, or E. coli, is responsible for millions of bacterial infections in women and the elderly, according to new research released today, Fox News reports.

The strain, H30-Rx, has the unprecedented ability to spread from the urinary tract into the blood, giving rise to sepsis, the most lethal form of infection.

Researchers say the strain poses a threat to more than 10 million Americans who suffer from urinary tract infections (UTIs).

The research, published in the American Society for Microbiology's journal mBio, shows how this bacteria has evolved from a single strain, allowing it to get around the most potent antibiotics available.

The research was led by Lance B. Price, a professor of environmental and occupational health at the George Washington University School of Public Health and Health Services. 

He and fellow researchers James R. Johnson of the Veterans Affairs Medical Center and the University of Minnesota, and Evgeni V. Sokurenko of the University of Washington School of Medicine, focused on the ST131 group of E. coli.

For example, researchers said that a strain known as H30 cloned itself into H30-R. This evolved to become fully resistant to the second-generation antibiotic ciprofloxacin, which was considered a wonder-drug in 1987. From there, the clones evolved into H30-Rx, which is resistant to even third-generation antibiotics like cephalosporins.

“This strain of E. coli spreads from person to person and seems to be particularly virulent,” Johnson said in a release. “This study might help us develop better tools to identify, stop or prevent its spread by finding better ways to block the transmission of the superbug, or by finding a diagnostic test that would help doctors identify such an infection early on—before it might have the chance to turn lethal.”

“We now know that we are dealing with a single enemy, and that by focusing on this strain we can have a substantial impact on this worldwide epidemic,” Sokurenko said.