Analysis of Novel Mass Spectrometry Diagnostics for Clinical Microbiology

Abstract

To optimally manage bloodstream infections, quick and appropriate antimicrobial treatment is critical. Rapid diagnostic testing (RDT) can help guide antimicrobial therapy in a timely and reliable fashion. Use of RDT in clinical microbiology is associated with improved patient outcomes including decreased mortality, morbidity, time of hospital stay, and patient costs. The ideal RDT is accurate, rapid, identifies antimicrobial resistance, is easy to use, and low cost. For septic patients, time to appropriate antimicrobial therapy is inversely related to the patient’s survival; therefore, fast, and accurate RDT is especially important. Several different types of RDT assays exist, including polymerase chain reaction, nanoparticle probe technology, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). MALDI-TOF MS is a mainstay diagnostic technology that has revolutionized the world of clinical microbiology. MALDI-TOF MS methods are high-throughput and have extensive pathogen panels. Microorganisms can be identified by MALDI-TOF MS once growth in culture is visible, thereby providing a decrease in both pathogen identification and time to effective antimicrobial therapy. Limitations of current MALDI-TOF MS diagnostics include limited ability in the identification of antimicrobial resistance and time to identification of organism, typically requiring 24-48 hours of additional ex vivo culture after positive blood culture. Recently, novel MALDI-TOF MS based technologies have been developed to identify pathogens direct from positive blood culture bottles, eliminating the need for further culture; however, novel technologies need to be evaluated and compared to current methods to provide valuable insight about the use of these diagnostics in clinical microbiology laboratory settings. This study addresses current limitations of MALDI-TOF MS diagnostics. In Specific Aim 1, a novel lipid-based technique termed Fast Lipid Analysis Technique (FLAT) was evaluated for its clinical utility in identifying colistin resistant Enterobacter species and Klebsiella aerogenes utilizing MALDI-TOF MS. For Specific Aim 2, positive patient blood cultures were prospectively collected from the University of Maryland Medical Center (UMMC) clinical microbiology laboratory to evaluate and compare the FDA-approved Bruker MBT Sepsityper® to other FDA-approved direct-from-blood culture RDTs. Finally, Specific Aim 3 compared the use of FLAT for direct-from-blood culture identification to the other previously compared RDTs using the novel Benefit-risk Evaluation for Diagnostics Framework (BED-FRAME).