Microbial Identification Using MALDI-TOF MS

Authors: Heather MacDonald, M(ASCP), MB(ASCP) and Robert C. Jerris, PhD, D(ABMM)
Reviewer: Rita Austin, DHEd, MLS(ASCP)CM, SMCM
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Continuing Education Credits

P.A.C.E.® Contact Hours: 1 hour(s)

Florida Board of Clinical Laboratory Science CE Credit Hours

Florida Board of Clinical Laboratory Science CE - General (Molecular Pathology): 1 hour(s)

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This course will briefly describe the basic principles of MALDI-TOF MS through the pre-analytical, analytical, and post-analytical phases and update the laboratorian to current applications of this technique.

Objectives

  • Define matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS).
  • Name the three major functional components of the MS instrument.
  • Describe two ways to justify purchase/acquisition of a MALDI-TOF MS system.
  • List three key technical methods used in preparing organisms for identification by MALDI-TOF MS.
  • Describe microbial growth requirements (media and incubation parameters) suitable for analysis by MALDI-TOF MS.
  • Identify key processes for postexamination reporting.
  • Summarize current regulatory requirements when performing MALDI-TOF MS.

Course Outline

  • Introduction to MALDI-TOF MS
    • Introduction
  • MALDI-TOF MS: Basic Concept
    • Basic Concept
    • Place the steps below in sequential order, as they would occur when using MALDI-TOF MS technology.
  • Preexamination
    • Preexamination Considerations
  • Cost Justification
    • Cost Justification
    • True or False: Using MALDI-TOF MS identification for early diagnosis of gram negative bacteremia increases the result turnaround time by 48 hours when compared to phenotypic tests.
  • Selection of Instrument
    • Instrument Selection
    • Instrument Comparison
    • Instrument Comparison, continued
    • What are the three major components of a MALDI-TOF MS instrument?
    • True or False: MALDI-TOF MS instruments are used exclusively in the research setting and when using them in the clinical laboratory to report identifications, they require a special comment about laboratory-developed tests (LDTs).
    • Which of these MALDI-TOF MS systems are FDA-cleared and available in the United States?
  • Regulation, Accreditation, and Best Practice
    • Food and Drug Administration (FDA)
    • College of American Pathologists (CAP)
    • Verification and Validation of MALDI-TOF MS Performance
    • True or False: Clinical laboratories must verify or validate instrumentation and the associated databases prior to utilization for clinical diagnostics.
    • MALDI-TOF MS can be used to identify which of the following organisms?
  • Examination
    • Test Performance
      • Template (Target Plate)
    • Growth and Incubation Requirements
      • Media: Solid versus Liquid
      • Selective versus Nonselective Culture Media
      • Incubation Conditions
      • True or False: When making a MALDI-TOF run, care must be taken in picking a colony from plated media, to avoid carryover of media proteins and other interfering substances.
    • Preparation/Extraction Techniques
      • Specimen Preparation
      • Direct Spotting
      • On-Plate Extraction Method (Formic Acid Overlay)
      • Full Extraction (In-Tube, Ethanol, Formic Acid Method)
    • Matrix
      • Matrix
    • Workflow
      • Key Workflow Factors: LIS and Instrument Interface
      • Key Workflow Factors: Centralized versus Decentralized MALDI-TOF MS Processing
      • True or False: The decentralized approach best describes the type of workflow that relies on a single laboratory station to process the target plate.
    • Quality Control
      • Quality Control Measures
      • What approximate concentration of organism is needed in order to achieve a valid identification?
    • Direct from Blood Culture MALDI-TOF MS
      • Identification from Positive Blood Culture Bottles
      • The MALDI-TOF MS can identify which of the following organisms from positive blood cultures?
    • Postexamination
      • Postexamination Considerations
      • True or False: Shigella and Escherichia coli are so closely related that they cannot be distinguished by MALDI-TOF MS.
      • True or False: Because of the extensive database, many organisms identified by MALDI-TOF MS in the clinical laboratory may not be familiar to laboratory scientists.
    • Safety
      • Safety Considerations
      • True or False: When performing the MALDI-TOF MS procedure, each chemical used should have a safety data sheet.
    • Summary
      • Summary
    • References
      • References

Additional Information

Level of Instruction: Intermediate
Author Information: 
Heather MacDonald, M(ASCP), MB(ASCP) has over 10 years of clinical laboratory experience and oversees a Molecular Diagnostics Laboratory. She is currently the Advanced Diagnostics Manager for Children's Healthcare of Atlanta in Georgia. Along with performing routine diagnostic assays, implementing laboratory-developed qualitative and quantitative molecular assays (both singleplex and multiplex) is her primary focus. Heather has published numerous articles and presents her research at national and international meetings. She has also worked with numerous corporations to bring commercial assays to market.
Robert C. Jerris, PhD, D(ABMM) is currently the Medical Director of Clinical Microbiology at Children's Healthcare of Atlanta in GA. He is also an Adjunct Associate Professor at the Emory University School of Medicine, in Atlanta, GA. Dr. Jerris has directed clinical microbiology and molecular diagnostic laboratories for over 30 years. In that time, he has developed and brought to market a number of clinical laboratory systems and assays. He is well published and presents his research at national and international meetings. As the current Chair of the American Society for Microbiology's Professional Affairs Committee, Dr. Jerris is committed to the workforce and regulatory oversight for clinical laboratories.
Reviewer Information: Rita Austin, DHEd, MLS(ASCP)CM, SMCM has been teaching in the Medical Laboratory Science Department at Farmingdale State College (part of the State University of New York) for 13 years and currently holds the rank of Associate Professor. She has been responsible for the development and delivery of all Clinical Microbiology content and also teaches Laboratory Research and Education. She has facilitated the Blood Bank and Immunology Laboratory courses as well. She maintains her expertise through continued practice as a per diem NY State Licensed Clinical Laboratory Technologist in a local Health System's Regional Microbiology Laboratory where her employment spans 36 years. Her BS degree in Medical Technology was earned in 1987 at New York Institute of Technology. She earned her MS in Medical Biology with a specialization in Microbiology from Long Island University in 2009, and her Doctorate in Health Education from A.T. Still University's College of Graduate Studies in 2019. She is certified by the ASCP as a Medical Laboratory Scientist and as a Specialist in Microbiology. Research interests include Interprofessional Education which has resulted in a publication and several poster presentations. She has participated in several textbook reviews and has co-authored chapters in a microbiology textbook.
Course Description:  This course will briefly describe the basic principles of MALDI-TOF MS through the preexamination, examination, and postexamination phases and update the laboratorian to current applications of this technique.