Confirmation and Identification of Salmonella spp., Cronobacter spp., and Other Gram-Negative Organisms by the Bruker MALDI Biotyper Method: Collaborative Study Method Extension to Include Campylobacter Species, Revised First Action 2017.09 (2019)

<i>Background:</i> The Bruker MALDI Biotyper<sup>®</sup> method utilizes matrix-assisted laser desorption/ionization time-of-flight MS for the rapid and accurate identification and confirmation of Gram-negative bacteria from select media types. The alternative method was evaluated in a method extension study of AOAC INTERNATIONAL <i>First Action Official Method</i><sup>SM</sup> 2017.09 using nonselective and selective agars to identify <i>Cronobacter</i> spp., <i>Salmonella</i> spp., <i>Campylobacter</i> 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. <i>Methods:</i> Two collaborative studies were organized, one in the United States focusing on <i>Cronobacter</i> spp. and other Gram-negative bacteria and one in Europe focusing on <i>Salmonella</i> spp. and other Gram-negative bacteria. Fourteen collaborators from seven laboratories located within the United States participated in the first collaborative study for <i>Cronobacter</i> spp. Fifteen collaborators from 15 service laboratories located within Europe participated in the second collaborative study for <i>Salmonella</i> spp. For each target organism (either <i>Salmonella</i> spp. or <i>Cronobacter</i> spp.), a total of 24 blind-coded isolates were evaluated. In each set of 24 organisms, there were 16 inclusivity organisms (<i>Cronobacter</i> spp. or <i>Salmonella</i> spp.) and 8 exclusivity organisms (non-<i>Cronobacter</i> spp. and non-<i>Salmonella</i> spp. closely related Gram-negative organisms). For the <i>Campylobacter</i> spp. method extension, 17 collaborators from eight laboratories located within the United States (seven laboratories) and Canada (one laboratory) participated in the collaborative study. A total of 24 blind-coded isolates were evaluated. In each set of 24 organisms, there were 16 inclusivity organisms (<i>Campylobacter</i> spp.) and 8 exclusivity organisms (non-<i>Campylobacter</i> spp. closely related Gram-negative organisms). <i>Results:</i> 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 <i>Cronobacter</i> study and a percentage of 100.0% to the genus level for the <i>Salmonella</i> study. For the <i>Campylobacter</i> method extension, a correct identification and confirmation rate of 100.0% was obtained for the <i>Campylobacter</i> organisms at the species level. For non-<i>Cronobacter,</i> non-<i>Salmonella</i>, and non-<i>Campylobacter</i> organisms, 100.0% were correctly identified. <i>Conclusions:</i> The results indicated that the alternative method produced equivalent results when compared to the confirmatory procedures specified by each reference method. <i>Highlights:</i> The method extension can be modified to include the identification and confirmation of <i>Campylobacter jejuni</i>, <i>Campylobacter coli</i>, and <i>Campylobacter lari</i>.