ERP Micro December 2019

1614  B astin et al . : J ournal of AOAC I nternational V ol . 102, N o . 5, 2019

Tables 2017.09A–J summarize the interlaboratory results per isolate for Salmonella, Cronobacter , and Campylobacter . Detailed results for each collaborator are presented in Tables 201709.K–T . Individual collaborator and sample results are presented in the Supplemental Information Tables 1–6.

correctly confirmed and/or identified, producing a correct identification rate of 95.5%. Misidentifications were observed for the following species: Enterobacter amnigenus, E. cloacae , and Enterobacter gergoviae . Exclusivity results: MALDI Biotyper method .—For all isolates that grew, 322 out of 323 isolates were correctly identified following the Bruker MALDI Biotyper method, producing a correct identification rate of 99.7%. One participant did not provide an identification result for the strain Serratia marcescens QL110071 isolated on CCI agar; the DT procedure was repeated and the eDT was run as described in the MALDI Biotyper workflow, but despite the fact that no identification result was obtained, no EXT protocol was run to complete the described MALDI Biotyper workflow. Across several participants, there were a total of 13 organisms for which no growth was observed on selective culture media. These organisms could not be analyzed by the alternative method. Exclusivity results: reference method .—When confirmed following the reference method, 112 out of 112 isolates were correctly excluded as Cronobacter species, producing a correct confirmation rate of 100.0%. For all isolates that contained growth, the reference method correctly identified 105 out of 112 isolates, producing a correct identification rate of 93.8%. Four of the participants obtained a Chromobacterium violaceum result for Pseudomonas aeruginosa ATCC 35032, one participant obtained a result of Citrobacter farmeri for Escherichia coli ATCC 10536, and seven participants obtained a result of E. cloacae for C. farmeri ATCC 51633 following the traditional confirmatory reference methods. Detailed confirmation and identification results are presented in Tables 2017.09E–H and Table 2 of the Supplemental Information. Inclusivity results: MALDI Biotyper method .—For the target organisms (inclusivity) analyzed, 1040 out of 1040 isolates were correctly confirmed and/or identified at both the genus and species levels following the Bruker MALDI Biotyper method, producing a correct identification rate of 100.0%. For some of the participants, growth of the target organisms was not able to be obtained from each selective agar. Two of the participants (participants 16 and 17) did not test from the mCCDA for three isolates, as they obtained limited to no growth for each isolate. Another participant (participant 3) began the analysis but was not able to complete testing for each isolate because of an emergency schedule conflict. Two participants (participants 6 and 13) were not able to obtain viable growth for the Campylobacter isolates from mCCDA for three isolates. One participant (participant 9) was unable to obtain growth for two Campylobacter lari isolates off of RCA, and one participant (participant 13) was not able to obtain viable growth of a Campylobacter jejuni isolate from CCA. Inclusivity results: reference methods .—When analyzed following the reference method, the recovery of the tested strains was only conducted from the nonselective CBA agar. Out of the 272 isolates, 272 were correctly confirmed and/or identified, producing a correct identification rate of 100.0%. Exclusivity results: MALDI Biotyper method .—For the non- Campylobacter isolates (exclusivity), 300 out of 300 isolates were correctly identified as non- Campylobacter organisms, and Campylobacter

Salmonella

Inclusivity results: MALDI Biotyper method .—For the target organisms (inclusivity) analyzed, 719 out of 719 isolates were correctly confirmed and/or identified following the Bruker MALDI Biotyper method, producing a correct identification rate of 100.0%. For one of the participants, Salmonella Newport Ad540 was not tested on RSA. Inclusivity results: reference method .—When analyzed following the reference method, 238 out of 239 isolates were correctly confirmed and/or identified, producing a correct identification rate of 99.6%. Salmonella Saintpaul A00C002 was misidentified as Aeromonas hydrophila by one participant following the traditional reference methods. Exclusivity results: MALDI Biotyper method .—For the nontarget organisms (exclusivity), 355 out of 355 isolates were correctly confirmed as non- Salmonella organisms, and each organism’s true identification was correctly identified following the Bruker MALDI Biotyper methodology, producing a correct confirmation rate and identification rate of 100.0%. For multiple participants, four of the organisms did not grow on RSA, and one organism did not grow on XLD; these organisms were, therefore, not analyzed from those media. Exclusivity results: reference method .—When confirmed following the reference method, 117 out of 120 isolates were correctly excluded as Salmonella species, producing a correct confirmation rate of 97.5%. For all isolates that grew, the reference method correctly identified 105 out of 120 isolates, producing a correct identification rate of 87.5%. The traditional confirmatory reference methods had significant difficulty identifying Escherichia hermanii Ad457, with 10 incorrect identifications. Yersiniaenterocolitica A00C066wasmisidentified once as Klebsiella oxytoca , Cronobacter sakazakii Ad1418 was misidentified once as Enterobacter cloacae, and A. hydrophila Ad1570 was misidentified by one participant as Vibrio fluvialis following the traditional confirmatory reference methods. There were three instances when Citrobacter braakii Ad2701 was incorrectly identified as Salmonella enterica arizonae following the traditional confirmatory reference methods. Some discrepant results were also observed for the oxidase test (three participants) or the Gram staining (one participant). Detailed results are presented in Tables 2017.09A–D and Table 1 of the Supplemental Information. Inclusivity results: MALDI Biotyper method .—For the target organisms (inclusivity), 671 out of 671 isolates were correctly confirmed and/or identified following the Bruker MALDI Biotyper method, producing a correct identification rate of 100.0%. For one of the participants, Cronobacter condimenti QL17031.1 did not contain growth on CCI and was not analyzed by the alternative method. Inclusivity results: reference method .—When analyzed following the reference method, 214 out of 224 isolates were Cronobacter