ERP Micro December 2019

B astin et al . : J ournal of AOAC I nternational V ol . 102, N o . 5, 2019  1601

Table 2017.09D. Summary of results for the confirmation of Gram-negative organisms ( Salmonella exclusivity)

MALDI Biotyper correctly confirmed

Ref. correctly confirmed

MALDI Biotyper incorrectly confirmed as Salmonella spp.

Ref. incorrectly confirmed as Salmonella spp.

MALDI Biotyper not tested

MALDI Biotyper total

Ref. total

Organism a

Providencia stuartii Ad1575 Citrobacter braakii Ad2701 Cronobacter sakazakii Ad1418 Yersinia enterocolitica A00C066 Aeromonas hydrophila Ad1570 Escherichia hermanii Ad457 Plesiomonas shigelloides Ad673 Serratia marcescens Ad447

45 45 45 44 42 45 44 45

15 12 15 15 15 15 15 15

0 0 0 0 0 0 0 0 0

0 3 0 0 0 0 0 0 3

0 0 0 1 3 0 1 0 5

45 45 45 44 42 45 44 45

15 15 15 15 15 15 15 15

117 b

355 c

120 d

Total isolates

355

a  ADRIA Développement collection, Quimper, France. b  117 isolates correctly confirmed as non- Salmonella , and 105 isolates correctly identified. c  The total numbers represent isolates analyzed on the three recommended culture media: Tryptic Soy Agar, Xylose Lysine Deoxycholate and RAPID’Salmonella. d  Reference method performed from the nonselective Tryptic Soy Agar plates only.

Table 2017.09E. Summary of results for the identification of Cronobacter (inclusivity)

MALDI Biotyper correctly identified

Ref. correctly identified

MALDI Biotyper incorrectly identified

Ref. incorrectly identified

Selective media no growth

MALDI Biotyper total

Ref. total

Organism

Cronobacter condimenti QL17031.1 a Cronobacter dublinensis QL17031.2 Cronobacter dublinensis CCUG 58094 b Cronobacter malonaticus QL123015.1A Cronobacter malonaticus CCUG 28859 Cronobacter muytjensii ATCC 51329 c Cronobacter sakazakii CCUG 21205 Cronobacter sakazakii CCUG 28857 Cronobacter sakazakii CCUG 28867 Cronobacter sakazakii CCUG 28870 Cronobacter sakazakii FSL F6-023 d Cronobacter sakazakii FSL F6-032 Cronobacter sakazakii FSL F6-038 Cronobacter sakazakii FSL F6-041 Cronobacter sakazakii FSL F6-046 Cronobacter sakazakii FSL F6-051

41 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

14 14 14 12 14 13 14 14 13 12 11 14 14 14 13 14

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 2 0 1 0 0 1 2 3 0 0 0 1 0

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

41 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14

1 e

671 f

224 g

Total isolates

671

214

10

a  QL = Q Laboratories collection (Cincinnati, OH). b  CCUG = Culture Collection University of Gothenburg (Gothenburg, Sweden). c  ATCC = American Type Culture Collection biological materials resource (Manassas, VA). d  FSL = Collection of the Food Safety Laboratory, Cornell University (Ithaca, NY). e  No growth on CCI only. f  The total numbers represent isolates analyzed on the three recommended culture media: Tryptic Soy Agar, Cronobacter Chromogenic Isolation Agar, and Enterobacter sakazakii Isolation Agar. g  Reference method performed from Tryptic Soy Agar only.

The matrix absorbs laser energy and transfers protons to the intact proteins or peptides in the gas phase. These ions are electrostatically accelerated and arrive in the flight tube at a mass-dependent speed. Because different proteins/peptides

fingerprinting using MALDI–TOF MS. First, the MALDI process transforms the proteins and peptides from the isolated microorganisms into positively charged ions. This is achieved by irradiating the matrix-sample composite with a UV laser.