Abstract
The prompt and accurate identification of bacterial pathogens is fundamental to patient health and outcome. Recent advances in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) have revolutionized bacterial identification in the clinical laboratory, but uniform incorporation of this technology in the U.S. market has been delayed by a lack of FDA-cleared systems. In this study, we conducted a multicenter evaluation of the MALDI Biotyper CA (MBT-CA) System (Bruker Daltonics Inc, Billerica, MA) for the identification of aerobic gram-negative bacteria as part of a 510(k) submission to the FDA. A total of 2,263 aerobic gram negative bacterial isolates were tested representing 23 genera and 61 species. Isolates were collected from various clinical sources and results obtained from the MBT-CA System were compared to DNA sequencing and/or biochemical testing. Isolates that failed to report as a "high confidence species ID" [log(score) ≥2.00] were re-tested using an extraction method. The MBT-CA System identified 96.8% and 3.1% of isolates with either a "high confidence" or a "low confidence" [log(score) value between 1.70 and <2.00] species ID, respectively. Two isolates did not produce acceptable confidence scores after extraction. The MBT-CA System correctly identified 99.8% (2,258/2,263) to genus and 98.2% (2,222/2,263) to species level. These data demonstrate that the MBT-CA System provides accurate results for the identification of aerobic gram-negative bacteria.
Highlights
The early and accurate identification of bacterial infections is crucial to patient care to help guide antimicrobial therapy
Molecular assays allow for the rapid identification that can eliminate the need for bacterial subculture [2, 3]
MALDI-TOF MS protocols were developed two decades ago to analyze whole bacterial cells, but the technology has only recently been used for routine identification [4, 5]
Summary
The early and accurate identification of bacterial infections is crucial to patient care to help guide antimicrobial therapy. Clinical laboratories have routinely identified pathogenic bacteria by using a combination of bacterial culture and biochemical tests. Molecular assays are only capable of identifying organisms targeted by the test, are more costly than culture, and have higher complexity compared to standard biochemical identification methods. Routine identification by MALDI-TOF MS is performed by generating mass spectra from whole bacterial cells composed primarily of ribosomal proteins [6, 7]. These protein profile spectra are compared to a reference library comprised of a wide range of organisms resulting in accurate species specific bacterial identification [7,8,9]. In 2008, the first commercially-available MALDI-TOF systems were available for research purposes; the lack of FDA-cleared systems has delayed incorporation into routine clinical microbiology laboratory practice in the United States [11,12,13]
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