New test identifies antibiotic-resistant bacteria in 30 minutes

Updated 2017-10-09 10:03:53 Xinhua

Scientists have pioneered a method to detect antibiotic susceptibility for urinary tract infections in less than 30 minutes, potentially enabling patients to be diagnosed and prescribed effective treatments during a single clinical visit.

The new test developed at California Institute of Technology that identifies antibiotic-resistant bacteria could shorten wait times from 3 days to less than 30 minutes and could help reduce the spread of superbug bacteria, according to the study published this week in Science Translational Medicine.

The discovery of antibiotics in the early part of the 20th century changed modern medicine. Simple infections that previously killed people became easy to treat. But because of overuse and misuse, antibiotics are losing their effectiveness.

Many species of bacteria have evolved resistance to commonly used antibiotics and multidrug-resistant bacteria--so-called superbugs--have emerged, plaguing hospitals and nursing homes. Last month, the World Health Organization issued a dire warning: The world is running out of antibiotics.

"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," Nathan Schoepp, co-author of the study, said in a statement.

According to the Caltech team, when treating bacterial with bacterial infections, doctors tend to ignore first-line antibiotics like methicillin or amoxicillin--drugs that bacteria are more likely to be resistant and skip straight to the stronger stuff, like ciprofloxacin.

They do that because there's a high chance that the weaker drugs won't work, but it is not ideal. That's because the increased use of second-line antibiotics makes it more likely that bacteria also will become resistant to these stronger drugs. Worryingly, scientists are warning that our last line of defense is beginning to fail.

However, there has not been a quick and easy way for a doctor to know if their patient's infection is resistant to particular antibiotics. Normally, to find out, the doctor would have to send a sample to a testing lab, and wait two to three days for an answer.

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.

They focused on one of the most common types of infections in humans, urinary tract infections (UTIs), which account for almost 8 million primary care visits every year (and almost always require antibiotics). However, the emergence of bacterial resistance remains a growing threat to global health, rendering many antibiotics ineffective, researchers say.

Researchers used a highly sensitive single-molecule DNA amplification and quantification technique called dLAMP to directly count bacterial genomes in urine samples. To perform the assay, urine samples were diluted and incubated for 15 minutes before dLAMP analysis to calculate ratios of bacterial DNA concentrations between untreated (without antibiotics) and treated (with antibiotics) samples.

The test operates on the principle that typical bacteria will replicate their DNA (in preparation for cellular division) less well in an antibiotic solution, resulting in the presence of fewer DNA markers. However, if the bacteria are resistant to the antibiotic, their DNA replication will not be hampered and the test will reveal similar numbers of DNA markers in both the treated and untreated solutions, scientists say.

Using 54 urine samples from patients with the bacteria Escherischia 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, Caltech's Ethel Wilson Bowles and Robert Bowles Professor of Chemistry and Chemical Engineering and director of the Jacobs Institute for Molecular Engineering for Medicine.

"We can change the world with a rapid test like this. We can change the way antibiotics are prescribed."

Researchers plan to begin running the test on other types of infectious bacteria to see how well it performs. They also hope to tweak the testing procedures to work with blood samples.

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