ERP Micro December 2019

1604  B astin et al . : J ournal of AOAC I nternational V ol . 102, N o . 5, 2019

Table 2017.09J. Summary of results for the confirmation identification of non- Campylobacter Gram-negative organisms (exclusivity)

MALDI Biotyper correctly identified

Ref. correctly identified

MALDI Biotyper incorrectly identified

Ref. incorrectly identified as Campylobacter

MALDI Biotyper total

MALDI Biotyper not tested

Ref. not tested

Ref. total

Organism

Citrobacter farmeri ATCC 51633 a Shimwellia blattae ATCC 29907 Edwardsiella tarda QL 11007.11 b Enterobacter aerogenes ATCC 35029 Escherichia hermannii ATCC 33651 Klebsiella oxytoca ATCC 43165 Proteus mirabilis QL 11007.6 Serratia marcescens QL 11007.1

44 22 56 25 33 43 45 31

17 17 17 17 17 17 17 17

0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0

24 46 12 43 35 25 23 37

0 0 0 0 0 0 0 0 0

44 22 56 25 33 43 45 31

17 17 17 17 17 17 17 17

299 c

136 d

Total isolates

299

136

245

a  ATCC = American Type Culture Collection biological materials resource (Manassas, VA). b  QL = Q Laboratories collection (Cincinnati, OH). c  The total numbers represent isolates analyzed on the four recommended culture media: Columbia Blood Agar, modified Charcoal Cefoperazone Deoxycholate Agar, RAPID’ Campylobacter Agar, and Campy Cefex Agar. d  Reference method performed from Columbia Blood Agar only.

Table 2017.09K. Comparative results for the identification of Salmonella

Candidate Tryptic Soy Agar

Candidate Xylose Lysine Deoxycholate

Candidate RAPID’ Salmonella Agar

Ref. Tryptic Soy Agar

N  a

X  b

Percent PA c

Target

Collaborator

Percent PA

Percent PA

Percent PA

N X

N X

N X

Salmonella species

1 2 3 4 5 6 7 8 9

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

16 16 16 16 15 15 d 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16 16

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

16 16 16 16 16 16 16 16 16 16 16 16 16 16 15 15 e 16 16 16 16 16 16 16 16 15 16 16 16 16 16

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.94 1.00 1.00

10 11 12 13 14 15

a N = Number of correct identifications. b X = Total number of isolates tested. c  PA = Positive agreement. d  No growth observed on agar for one isolate. e  Isolate not tested.

have different masses, ions arrive at the detector at different times (TOF). The MALDI Biotyper System measures the time (in the nanosecond range) between pulsed acceleration and the corresponding detector signal of the ions, and the time is converted into an exact molecular mass. The highly abundant microbial ribosomal proteins result in a mass spectrum with a characteristic mass and intensity distribution pattern. This pattern is species-specific for many bacteria, yeasts, and molds and can be used as a “molecular

fingerprint” to identify a test organism. The mass spectra are transformed into peak lists by the MALDI Biotyper software and are compared to the patterns in the reference library.

B. Apparatus and Reagents Items (a)–(j) are available from Bruker Daltonik GmbH (Bremen, Germany).