MALDI-TOF MS Applied to Indirect Carbapenemase Detection: A Validated Procedure to Clearly Distinguish Between Carbapenemase-Positive and Carbapenemase-Negative Bacterial Strains

Lijun Wang, Chao Han, Wenjun Sui, Mei Wang, Xinxin Lu

Anal Bioanal Chem. 2013 Jun;405(15):5259-66.

PMID: 23584712

Abstract:

Laboratory identification of carbapenemase-producing clinical isolates is crucial to limit the spread of the bacteria. In this study, we shall first develop the matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) assay in automatic identification of carbapenemase producers. A total of 143 well-characterized isolates were studied. After an incubation of bacteria with meropenem trihydrate, the mixture was centrifuged and the supernatant analyzed by MALDI-TOF MS. A genetic algorithm model with ClinProTools software was built using spectra of 43 carbapenemase-positive isolates and 40 carbapenemase-negative isolates after 2 h of incubation. This model was externally validated using 60 test isolates. All spectra of supernatants of the carbapenemase-negative isolates showed peak profiles comparable to that of pure meropenem (m/z 384.159, 406.140, and 428.122 of its two sodium salt variants) regardless of the incubation time tested. For the carbapenemase-positive isolates, the specific peak for meropenem at m/z 384.159 disappeared during the incubation time, two products of meropenem degradation were identified with m/z 358.18 (the decarboxylated product) and 380.161 (sodium salt of the decarboxylated product), and other degradation products were observed (native molecule with disrupted amide bond with m/z 402.169, three sodium salt variants with m/z 424.151, 446.133, and 468.115). Sixty test isolates were 100% correctly classified as carbapenemase positive and carbapenemase negative with the genetic algorithm model. MALDI-TOF MS coupled with ClinProTools is capable of rapidly, accurately, and automatically identifying carbapenemase producers.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP119478567-A	Meropenem trihydrate		119478-56-7	Price

Catalog Number

Product Name

Structure

CAS Number

Price

AP119478567-A

Meropenem trihydrate

119478-56-7

Price

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