Mass Spec Technology to Transform Pathogen Identification, Improve Clinical Care

With the U.S. Food and Drug Administration’s August clearance, VITEK MS from bioMerieux (Durham, N.C., and France) became the first mass spectrometry-based system approved for rapid clinical identification of 193 microorganisms. The technology enables significantly more rapid bacterial and fungal identification and quicker drug susceptibility testing, which can improve anti-microbial management and decrease associated health care expenditures. While the term “game-changer” is often overused, experts agree that the use of mass spectrometry for bacterial identification has the potential to truly alter laboratory workflow and profoundly enhance timely clinical care by cutting the time needed for identification of microbial infectious agents from days to hours. “MALDI-TOF [matrix-assisted laser desorption/ionization-time of flight] will have one of the greatest impacts on clinical microbiology since the use of molecular amplification methods for the identification of pathogens,” said Christine C. Ginocchio, Ph.D., the senior medical director at North Shore-LIJ Health System Laboratories, whose lab has been investigationally using the system for a year. The system is based on Nobel prize-winning MALDI technology. The soft ionization technique uses a special matrix solution that prevents fragmentation of large molecules. The travel time of the charged molecules is measured with TOF directly proportional to the molecules’ mass. This is charted as a mass-to-charge ratio and compared to reference standards. In practice, a small sample from a culture plate is applied to a slide, covered with a drop of matrix solution, and inserted into the automated system. Microbial identification can be generated within minutes of ionization with comparable accuracy to nucleic acid sequencing.  

MALDI-TOF Saves Health Care Dollars

Rapid organism identification allows clinicians to prescribe the most appropriate treatment sooner and de-escalate empiric therapy from broad-spectrum agents that drive anti-microbial resistance. In an article published in the September issue of Archives of Pathology & Laboratory Medicine, researchers from the Methodist Hospital Research Institute (Houston) demonstrate that integration of rapid identification and susceptibility techniques with anti-microbial stewardship significantly improved time to optimal therapy and significantly decreased health care total costs.The researchers compared conventional microbiology laboratory methods to MALDI-TOF technology (Bruker Daltonics, Fremont, Calif.) in consecutive adult patients hospitalized with gram-negative blood cultures between Aug. 15, 2011, and Nov. 30, 2011 (preintervention period; 112 patients) and between Feb. 1, 2012, and May 25, 2012 (intervention period; 107 patients). Differences in hospital outcomes were assessed in survivors. Appropriateness of antibiotic therapy was evaluated by an infectious diseases–trained pharmacist and the index culture time-to-positivity (TTP) was assessed. The urinary tract was the most common infection source (42.9 percent in the preintervention group and 34.6 percent in the intervention group) and Escherichia coli was most frequently isolated (50 percent in preintervention and 43 percent in intervention group). Average time from the blood culture TTP to final species identification and anti-microbial susceptibility occurred nearly a full day quicker with MALDI-TOF (47.1 hours for the preintervention study group versus 24.4 hours for the intervention group). Overall, adjustments to antibiotic interventions occurred, on average, 75 hours from TTP in 80 percent of patients preintervention. The time dropped to 29 hours, on average, in 94 percent of patients during use of MALDI-TOF. Mean hospital length of stay was significantly longer in the preintervention group survivors (11.9 days versus 9.3 days in the intervention group). Mean hospital costs per patient were $45,709 in the preintervention group compared to $26,162 in the intervention group.

  In addition to critical time savings to the patient and clinical team resulting from significantly faster pathogen identification, the MALDI system saves the laboratory significant time. Within a matter of a few minutes from the time of a positive culture, a tech can set up for identification and susceptibility testing, and with up to four slides able to run at a time and results in a little over an hour, throughput is not a rate-limiting step, says Ginocchio, whose laboratory services 11 hospitals and can run nearly 250,000 to 300,000 microbial identification tests annually. Her lab will be using two MALDI systems, with one dedicated to stat testing. While bioMerieux estimates that there may be 800 U.S. labs with the volume to justify the VITEK MS system, laboratories that have tried the system see a financial case for adoption. In a small study based on investigational use of the system for limited volumes of testing, North Shore estimates that the system can save $150,000 in reagent costs and $130,000 in technologist savings annually. In addition to cost savings for the laboratory from improved workflow and the larger health system resulting from improved diagnosis and patient management, Bert Top, Ph.D., from bioMerieux USA, tells DTET that a number of factors are likely to drive adoption of MALDI-TOF systems—the increasing number of hospitalized patients with underlying conditions making them extremely vulnerable to hospital-acquired infections, the simultaneous increase in drug-resistant organisms, and the changing reimbursement landscape requiring laboratories and hospitals to provide higher-quality care for lower total costs. The first step in bioMerieux’s rollout strategy is to convert all of the company’s research and investigation sites into fully operational clinical sites, which is expected to be completed in the next couple of months. Takeaway: Mass spectrometry for bacterial identification has the potential to truly alter laboratory workflow and profoundly enhance timely clinical care by cutting the time needed for identification of microbial infectious agents from days to hours.