Bacteria cause 8.6 million UTIs annually in the United States. Antibiotics are the first line of defense, but microbes are rapidly evolving resistance to standard drugs. Ten percent of UTIs are now caused by strains of Escherichia coli bacteria that ward off a bevy of antimicrobial drugs using enzymes called extended-spectrum beta-lactamases.
Currently, diagnosis of these drug-resistant infections is expensive and takes days of growing the bacteria. The new exam requires about 20 minutes: Researchers add a red liquid that changes color with acidity to bacteria from urine samples. If the bacteria make the antidrug enzymes, the liquid’s acidity increases and the sample turns yellow. In a trial with 450 urine samples, the test’s accuracy – 98 percent – rivaled slower methods that grow bacteria. The new test costs $2 to $3 per sample.
The diagnostic may help doctors choose sooner rather than later antibiotics that still work against drug-resistant E. coli, said test codeveloper Laurent Dortet, a microbiologist at Bicêtre Hospitalin Le Kremlin-Bicêtre, France.
Editor’s Note: This article was updated September 26, 2014 to correct how long the new exam takes.