ERP Micro December 2019

B astin et al . : J ournal of AOAC I nternational V ol . 101, N o . 5, 2018  1593

MICROBIOLOGICAL Methods

Confirmation and Identification of Salmonella spp., Cronobacter spp., and Other Gram-Negative Organisms by the Bruker MALDI Biotyper Method: Collaborative Study, First Action 2017.09 B enjamin B astin , P atrick B ird , M. J oseph B enzinger , J r , E rin C rowley , J ames A gin , and D avid G oins Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214 D aniele S ohier 1 , M arkus T imke , G ongyi S hi , and M arkus K ostrzewa Bruker Daltonik GmbH, Fahrenheitstraße 4, 28359 Bremen, Germany

Submitted for publication January 10, 2018. This method was approved by the Expert Review Panel for Microbiology Methods for Food and Environmental Surfaces as First Action. The Expert Review Panel for Microbiology Methods for Food and Environmental Surfaces invites method users to provide feedback on the First Action methods. Feedback from method users will help verify that the methods are fit-for-purpose and is critical for gaining global recognition and acceptance of the methods. Comments can be sent directly to the corresponding author or methodfeedback@aoac.org. Supplemental information is available online at: http://aoac. publisher.ingentaconnect.com/content/aoac/jaoac 1 Corresponding author’s email: daniele.sohier@bruker.com States participated in the first collaborative study for Cronobacter spp. Fifteen collaborators from 15 service laboratories located within Europe participated in the second collaborative study for Salmonella spp. For each target organism (either Salmonella spp. or Cronobacter spp.), a total of 24 blind-coded isolates were evaluated. In each set of 24 organisms, there were 16 inclusivity organisms ( Cronobacter spp. or Salmonella spp.) and 8 exclusivity organisms (closely related The Bruker MALDI Biotyper ® method utilizes matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS for the rapid and accurate identification and confirmation of Gram-negative bacteria from select media types. The alternative method was evaluated using nonselective and selective agars to identify Cronobacter spp., Salmonella spp., and select Gram-negative bacteria. Results obtained by the Bruker MALDI Biotyper were compared to the traditional biochemical methods as prescribed in the appropriate reference methods. Two collaborative studies were organized, one in the United States focusing on Cronobacter spp. and other Gram-negative bacteria, and one in Europe focusing on Salmonella spp. and other Gram- negative bacteria. Fourteen collaborators from seven laboratories located within the United

non- Cronobacter spp. and non- Salmonella spp. Gram-negative organisms). After testing was completed, the total percentage of correct identifications from each agar type for each strain was determined at a percentage of 100.0% to the genus level for the Cronobacter study and a percentage of 100.0% to the genus level for the Salmonella study. For both non- Cronobacter and non- Salmonella organisms, a percentage of 100.0% was correctly identified. The results indicated that the alternative method produced equivalent results when compared to the confirmatory procedures specified by each reference method. C onfirmation and identification for foodborne pathogens following the biochemical tests specified in the traditional reference methods U.S. Food and Drug Administration (FDA)/ Bacteriological Analytical Manual (BAM) Chapter 29 (1), FDA/BAM Chapter 5 (2), U.S. Department of Agriculture (USDA)-Food Safety and Inspection Service (FSIS)/ Microbiology Laboratory Guidebook (MLG) 4.09 (3), and the International Organization for Standardization (ISO) 22964:2017 (4) and ISO 6579:2002 (5) can take anywhere from 3 to 7 days. This extended time can lead to delays in recalls and result in widespread outbreaks. With the Bruker MALDI Biotyper ® method, the time to result for accurate and reliable confirmation and identification from isolated colonies on selective and nonselective agars can be reduced to 30 min to 2 h for investigation of a full 96-spot target plate (6). The Bruker MALDI Biotyper method is designed to rapidly confirm (meaning to confirm the presumptive result of an alternative or a reference method) and identify (meaning to determine the identity of an analyte from a variety of agar plates). The method was validated for use with common nonselective, selective, and chromogenic agars following isolation of the organisms per the appropriate reference or proprietary method. Samples are analyzed using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS. The highly abundant microbial ribosomal proteins result in a mass spectrum with a characteristic mass and intensity distribution pattern. The generated spectrum pattern of these proteins is used to reliably and accurately identify a particular microorganism

DOI: https://doi.org/10.5740/jaoacint.18-0012