University of California, Santa Barbara scientists have developed an antibiotic susceptibility test (AST) in a study that revealed that some FDA-approved antibiotics — available at neighborhood pharmacies — can treat multidrug-resistant superbug infections.
The study, published last Thursday in the journal Cell Reports Medicine, may improve the way antibiotics are developed, tested, and prescribed, the authors said.
Their research, supported by the National Institutes of Health’s National Heart, Lung, and Blood Institute, and the U.S. Army Research Office, may also help fight antibiotic resistance by optimizing the prescription and use of currently available antibiotics, they said
Most physicians are aware of the flaws in standard tests. However, commercially available antibiotics are often not prescribed because standard tests predict they will not work.
"Here, we report the development of an alternative AST protocol for widespread clinical utility based on media that are more physiologically representative of in vivo infection conditions (mammalian cell culture medium, pooled human donor serum, or urine) vs. standard bacteriologic [Mueller-Hinton broth] medium," the authors wrote.
They sought to address what they viewed as a flaw in the healthcare paradigm for determining antibiotic resistance: It fails to account for environmental conditions in the body that may impact drug potency. By simulating body conditions, their test identified several effective antibiotics previously rejected by standard testing. Furthermore, when both the new and gold-standard tests agreed, researchers observed a nearly perfect prediction of treatment success or failure.
The study researchers conducted a screening of more than 500 antibiotic-bacteria combinations. Their findings indicate that the specified standard tests are incorrect about 15% of the time. Since physicians rely on these tests for treatment decisions, they may prescribe the wrong antibiotic. When recommended antibiotics do not work for their patients, physicians must rely on their experience to decide on more-appropriate antibiotics. This study may help address the disparity between antibiotics indicated by gold-standard testing and actual patient outcomes.
The researchers said that re-evaluating FDA-approved antibiotics may offer greater benefits than developing new drugs to combat antimicrobial resistance — it may save time and costs as well as lives. For example, treatments for sepsis — a life-threatening medical emergency stemming from the body's extreme response to infection — are expensive, and time- and labor-intensive. A test based on the new method could lead to reduced costs for the healthcare industry in efforts to identify drugs to fight antimicrobial-resistant infections, the researchers said, adding that more accurate testing may also reduce the costs of new drug discovery by streamlining the detection of lead candidates prior to conducting expensive human clinical trials.
“People are not Petri dishes—that’s why antibiotics fail,” Michael Mahan, co-author and UC Santa Barbara professor, said in a statement. “Testing under conditions that mimic the body improves the accuracy by which lab tests predict drug potency.”