Automated identification of 193 human illness initiators

In the US, the Food and Drug Administration has allowed marketing of the bioMérieux VITEK mass spectrometer system for automated identification of bacteria and yeasts that are known to cause serious illness in humans. The system can identify 193 different microorganisms and can perform up to 192 different tests in a single automated series of testing, with each test taking about one minute.

The VITEK MS can identify yeasts such as those from the Candida, Cryptococcus and Malassezia groups, and bacteria from the Staphylococcaceae, Streptococcaceae, Enterobacteriaceae, Pseudomonadaceae and Bacteroidaceae families, which are associated with skin infections, pneumonia, meningitis and bloodstream infections.

“The ability for laboratories to use one device to identify almost 200 different microorganisms is a significant advance in the timely identification of pathogenic microorganisms,” said Alberto Gutierrez, Ph, director of the Office of In Vitro Diagnostics and Radiological Health at FDA’s Center for Devices and Radiological Health. “Rapid identification of harmful microorganisms can improve the care of critically ill patients.”

The VITEK MS incorporates a technology called matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS). The technology uses a laser to break yeast and bacteria specimens into small particles that form a pattern unique to the microorganism. The VITEK MS automatically compares the microorganism pattern to 193 known yeasts and bacteria in the test system’s database to identify the microorganism.

Compared to other identification methods that require abundant organism growth for testing, mass spectrometry requires only a small amount of yeast or bacterial growth, so testing can start as soon as growth is visible, generally within 18 to 24 hours. Traditional methods can take up to five days to produce the same identification results.

The FDA reviewed the VITEK MS through its de novo classification process, a regulatory pathway for some novel low-to-moderate risk medical devices that are not substantially equivalent to an already legally marketed device.

For the de novo petition, the FDA based its decision on the results of a study of 7068 microorganisms. When compared to sequencing and biochemical testing, the VITEK MS correctly identified the scientific group or family 93.6% of the time (with 87.5% of microorganisms identified to species level). The VITEK MS provided a ‘no identification’ result for 3.2% of the microorganisms in the study. Of all test results, only 0.8% were incorrect and 2.4% were low discrimination with no correct result.

The VITEK MS is for clinical use for the identification of microorganisms cultured from human specimens. It is indicated for use in conjunction with other clinical and laboratory findings to aid in the diagnosis of bacterial and fungal infections.