ERP Micro December 2019

1598  B astin et al . : J ournal of AOAC I nternational V ol . 102, N o . 5, 2019

Exclusivity Organisms: Cronobacter

Table 3. Participation of each collaborating laboratory for Campylobacter

The exclusivity organisms consisted of non- Cronobacter Gram-negative organisms that were closely related to the target organisms. Each exclusivity organism in the Cronobacter study was subcultured onto three agars [CCI (Thermo Fisher Scientific or equivalent), ESIA (Bio-Rad or equivalent), and TSA (Bio- Rad or equivalent)] from the blind-coded stock culture tubes. The CCI plates were incubated for 20–26 h at 44 ± 2°C, the ESIA plates were incubated for 20–26 h at 41.5 ± 2°C, and the TSA plates were incubated for 18–24 h at 35–37 ± 1°C. Following incubation, if growth was present on an agar plate, an isolated colony was analyzed by the Bruker MALDI Biotyper using the DT technique. When needed, the eDT procedure was used or the tube extraction (EXT) if necessary to obtain a reliable result. To demonstrate the equivalency between the reusable target and the disposable target, both were used by different participants during the evaluation (Table 2). Growth from the TSA plate was also analyzed by conducting a spot oxidase test (Thermo Fisher Scientific) and by conducting biochemical confirmation analysis using either API 20E or GN VITEK 2 (AOAC OMA 2011.17 ). From the CBA, each isolate (target and nontarget) was subcultured onto four agars: CBA (Hardy Diagnostics or equivalent), mCCDA (Neogen or equivalent), RCA (Bio-Rad or equivalent), and CCA (Neogen or equivalent). The plates were incubated for 48 h at 41.5 ± 1°C under microaerobic conditions. Following incubation, growth present on each plate was analyzed by the Bruker MALDI Biotyper using the DT technique. When needed, the eDT procedure was used. If necessary, EXT was used to obtain a reliable (log score >1.7) result. To demonstrate the equivalency between the reusable target and the disposable target, both were used by different participants during the evaluation (Table 3). Growth from the Campylobacter Method Extension

Collaborator ID No.

Participating lab

Analyst

Target

Disposable a Disposable Reusable b Disposable Disposable Reusable Reusable Reusable Reusable Reusable Reusable Reusable Reusable Reusable Reusable Disposable

1 2 3 4 5 6 7 8 9

1 1 2 3 3 4 4 5 5 6 6 6 7 7 7 8 8

1 2 1 1 2 1 2 1 2 1 2 3 1 2 3 1 2

10 11 12 13 14 15 16 17

Disposable a  Disposable = Target that is for single use, and the MBT adapter is required. b  Reusable = Stainless-steel target that can be cleaned and used again. CBA plates was evaluated for corkscrew morphology and darting motility. Each isolate was also analyzed by a spot oxidase test (Thermo Fisher Scientific or equivalent), tested using the PanBio-Campy latex agglutination test kit (Scimedx Corp., Denville, NJ), and struck to a fresh CBA plate and incubated under aerobic conditions at 25 ± 1°C. Each collaborating laboratory reported bacterial identification results for each organism on the data sheets provided. The data sheets were submitted to the study director at the end of testing for statistical analysis. Data for each organism was analyzed to determine the percentage of accurate identification and the percentage of misidentification by the Bruker MALDI Biotyper Method and the reference method. Statistical Analysis

Table 2. Participation of each collaborating laboratory for Cronobacter

Collaborator ID No.

Participating lab

Analyst

Target

Disposable a Reusable b Reusable Reusable Reusable Disposable Disposable Reusable Reusable Reusable Reusable Disposable Disposable

1 2 3 4 5 6 7 8 9

1 2 2 3 3 4 4 5 5 6 6 7 7 7

1 1 2 1 2 1 2 1 2 1 2 1 2 3

AOAC Official Method 2017.09 Confirmation and Identification of Salmonella Species, Cronobacter Species, Campylobacter Species, and Other Gram-Negative Organisms Bruker MALDI

Biotyper Method First Action 2017 Revised First Action 2018

10 11 12 13 14

[Applicable to confirmation and identification of Salmonella species, Cronobacter species, Campylobacter species, and other Gram-negative organisms from select media types.] Caution: Follow all instructions carefully. Failure to do so may lead to inaccurate results. See Tables 2017.09A–J for a summary of results of the interlaboratory study.

Disposable a  Disposable = Target that is for single use, and the MBT adapter is required. b  Reusable = Stainless-steel target that can be cleaned and used again.