Direct Detection of KPC Peak from Positive Blood Cultures Using MALDI-TOF MS: Are We There Yet?

• Main Authors: Natália Kehl Moreira (Author), Camila Mörschbächer Wilhelm (Author), Aymê Duarte Echevarria (Author), Fabiana Caroline Zempulski Volpato (Author), Priscila Lamb Wink (Author), Afonso Luís Barth (Author), Juliana Caierão (Author)
• Format: Book
• Published: MDPI AG, 2023-03-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Detecting carbapenemase-associated carbapenem resistance is a subject of major clinical and epidemiological concern as it influences therapeutic choice. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been proposed as a means to assess bacterial resistance mechanisms. We aimed to detect the KPC enzyme directly from positive blood cultures using MALDI-TOF MS. To do so, 102 clinical <i>Enterobacteria</i> were evaluated, including 59 <i>bla</i>_KPC positives. Proteins were extracted using formic acid, isopropyl alcohol, and water (17:33:50) and spotted onto a steel target plate using the double-layer sinapinic acid technique. Two parameters were considered: (i) the visual detection of a clear peak with the expected KPC <i>m</i>/<i>z</i> and (ii) the evaluation of the relative intensity of the ions in the peak. A peak was observed in 56/59 <i>bla</i>_KPC-positive isolates (94.9% sensitivity), with no false-positive results (100% specificity). When considering intensity, with a cut-off ≥120 (a.u.), sensitivity was 94.9% and specificity was 95.3%. We proposed a "buffer" zone, with intermediate values of intensity (115 to 125) reaching 100% sensitivity and specificity. The detection of KPC peaks directly from positive blood cultures using MALDI-TOF MS is feasible and rapid, which may improve appropriate patient therapy and antimicrobial stewardship.

Item Description

10.3390/antibiotics12030601
2079-6382