The U.S. Food and Drug Administration (FDA) recently granted approval for a new testing system that can more quickly identify the microbe causing a bloodstream infection once a blood culture is positive. It is the first testing system that can rapidly determine which antibiotics are most effective for the given bacteria or yeast, according to the FDA.
Bacterial or yeast blood infections can occur in a patient of any age, but the infections are especially serious in infants, older adults and in people who have a weakened immune system. And without rapid treatment, bloodstream infections—known as bacteremia—can lead to septic shock and death. Currently, when healthcare practitioners suspect a bloodstream infection, they begin treatment with broad-spectrum antibiotics that will work against the most common pathogens.
Typically, blood cultures are used to test for microbes in the blood when bloodstream infections are suspected. The newly approved test system can identify, from positive blood cultures, 14 different species of bacteria and two species of yeast that commonly cause bloodstream infections. In the past, labs required a day or two to identify a pathogen causing a bloodstream infection. The new test gives results for microbe identification in an hour and a half. There are other test systems which can also identify bacteria rapidly. This test is unique because, in addition to identifying the offending pathogen, the test is able to rapidly determine which antibiotics are likely to successfully treat the infection. It does this in about six and a half hours instead of the traditional two days.
"By identifying organisms and knowing earlier which antibiotics the organism is likely to respond to, health care professionals can treat patients with bloodstream infections more appropriately," said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics and Radiological Health at the FDA's Center for Devices and Radiological Health. The advantages of this approach are that it reduces treatment with unnecessary antibiotics, while also switching to more effective antibiotics if the initial drug is found to be ineffective against the pathogen identified.
The new test works by comparing the genetic material of the pathogen in the bloodstream to DNA known to be unique to a specific bacteria or yeast. Once the exact microbe is known, it's mixed with antibiotics and the growth of the bacteria is measured by time-lapse images. If the presence of the antibiotic keeps the organism from growing, that can mean that the drug can potentially be used for treatment.
The FDA's approval was based on a clinical study of 1,850 positive blood cultures. In the study, the test correctly identified the bacteria or yeast in the blood culture 95% of the time. Per the FDA, testing for antibiotics was also accurate when compared with existing susceptibility tests.
The test did result in some false positives—meaning the test sometimes reported microbes when they weren't actually there, so the approval comes with a recommendation that the new test be corroborated by other lab tests as a backup.