Bacteria are evolving resistance to antibiotics at an alarming rate, and according to a report released last year these so-called superbugs could kill 10 million people a year by 2050 if we don't take action. One of the main issues is overprescription of antibiotics, and now a new test developed by scientists at Caltech could help doctors quickly prescribe the best type of antibiotic to fight a particular infection.

Preventing a return to "the dark ages of medicine" is a top priority for health organizations, and researchers are developing an arsenal of creative weapons in the war against superbugs. New gels and materials can kill them more effectively, while other techniques involve supercharging existing drugs or neutralizing the bugs without killing them. And of course, finding and developing new antibiotics is a key strategy.

The new test takes aim at one particular root of the problem: overprescription. According to the Caltech team, when treating bacterial infections in patients, doctors tend to ignore first-line antibiotics and skip straight to the stronger stuff. They do that because there's a high chance that the weaker drugs won't work, but the flipside is that this practice is causing bacteria to evolve resistance to the second-line drugs faster. Worryingly, scientists are warning that our last line of defense is beginning to fail.

"Right now, we're overprescribing, so we're seeing resistance much sooner than we have to for a lot of the antibiotics that we would otherwise want to preserve for more serious situations," says Nathan Schoepp, co-author of a study describing the new test.

Rather than doctors simply assuming that first-line antibiotics wouldn't work, the Caltech team's test was designed to allow them to quickly identify what bacteria is causing a particular infection, and prescribe a drug accordingly. Normally, tests of this kind can take up to three days, but time being of the essence, the new test can be completed in 30 minutes, meaning it can be performed during a single visit to the doctor.

As one of the most common types of bacterial infection, the team focused on urinary tract infections (UTIs) to develop the test. To check the resistance of any bacteria that might be present, a doctor first collects a urine sample from a patient with a UTI. Half of the sample is exposed to an antibiotic for 15 minutes, while the other half is tested without adding any drugs. Then, bacteria from both samples are run through a process to look for specific DNA markers.

That process combines a chemistry detection technique called dLAMP with a device called a SlipChip. In effect, the targeted DNA markers will show up on the SlipChip as fluorescent green spots, and the fewer of them there are, the more effective that antibiotic was against that bacteria. If the treated and non-treated samples have similar numbers of dots, the drug clearly had no effect. But if significantly fewer spots show up in the treated sample, then that antibiotic can be prescribed to the patient, saving the second-line drugs for more urgent cases.

Using 54 urine samples from patients with E. coli-caused UTIs, the researchers compared the results of their test to a standard test that normally takes two days. Their new method was found to be a 95 percent match to the results of the existing test.

"Therapies are driven by guidelines developed by organizations like the World Health Organization or the Centers for Disease Control and Prevention without knowing what the patient actually has, because the tests are so slow," says Rustem Ismagilov, co-author of the study. "We can change the world with a rapid test like this. We can change the way antibiotics are prescribed."

Next, the team plans to use the test to detect other bacteria besides E. coli, and tweak the method to work with blood samples as well.

The research was published in the journal Science Translational Medicine.

Source: Caltech

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