Establishing a quantitative index of meropenem hydrolysis for the detection of KPC- and NDM-producing bacteria by MALDI-TOF MS

• Published in: Journal of microbiological methods Vol. 187; p. 106268
• Main Authors: Wilhelm, Camila Mörschbächer, Forni, Giovanna de Ross, Carneiro, Maiara dos Santos, Barth, Afonso Luís
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-08-2021
• Subjects: Carbapenemase; Hydrolysis; KPC; MALDI-TOF MS; Meropenem; NDM; Hydrolysis; Carbapenemase; MALDI-TOF MS; Meropenem; NDM; KPC
• ISSN: 0167-7012; 1872-8359
• DOI: 10.1016/j.mimet.2021.106268

Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS), commonly used for microorganism identification, can also be applied for the detection of carbapenemase-producing bacteria by the evaluation of carbapenem hydrolysis. Since KPC- and NDM-producing bacteria are related to high mortality rates, diagnostic assays for its detection are essential. The aim of this study was to develop and evaluate a method to establish a quantitative measure (hydrolysis index - HI) to detect meropenem hydrolysis by MLADI-TOF MS.
blaKPC and blaNDM positive and negative Klebsiella pneumoniae isolates and Escherichia coli ATCC 25922 (control) were incubated in a meropenem solution for 2 h. Protein extraction from these suspensions were submitted to MALDI-TOF MS analysis. The intensity of peaks at 384 m/z and 379 m/z of each isolate were used to establish the HI as follows: HI = (Peak intensity384 Test / Peak intensity379 Test) / (Peak intensity384 Control / Peak intensity379 Control). Receiver Operating Characteristic curve was used to determine a cutoff value to differentiate carbapenemase-producing from carbapenemase non-producing bacteria.
As all carbapenemase-producing K. pneumoniae presented HI ≤0.55 and all carbapenemase non-producing isolates presented a HI ≥0.57, the index of 0.56 was established as a cutoff value to differentiate carbapenemase (KPC and NDM) producing and non-producing bacteria.
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•Carbapenemase-producing bacteria can be detected by MALDI-TOF MS.•The hydrolysis index efficiently determines production of KPC and NDM carbapenemases.•The hydrolysis index presents high sensitivity and specificity for detecting KPC and NDM producing bacteria.