A simple, robust and rapid approach to detect carbapenemases in Gram-negative isolates by MALDI-TOF mass spectrometry: validation with triple quadripole tandem mass spectrometry, microarray and PCR

Abstract

Carbapenemases should be accurately and rapidly detected, given their possible epidemiological spread and their impact on treatment options. Here, we developed a simple, easy and rapid matrix-assisted laser desorption ionization-time of flight (MALDI-TOF)-based assay to detect carbapenemases and compared this innovative test with four other diagnostic approaches on 47 clinical isolates. Tandem mass spectrometry (MS-MS) was also used to determine accurately the amount of antibiotic present in the supernatant after 1 h of incubation and both MALDI-TOF and MS-MS approaches exhibited a 100% sensitivity and a 100% specificity. By comparison, molecular genetic techniques (Check-MDR Carba PCR and Check-MDR CT103 microarray) showed a 90.5% sensitivity and a 100% specificity, as two strains of Aeromonas were not detected because their chromosomal carbapenemase is not targeted by probes used in both kits. Altogether, this innovative MALDI-TOF-based approach that uses a stable 10-μg disk of ertapenem was highly efficient in detecting carbapenemase, with a sensitivity higher than that of PCR and microarray.

Clinical Performance of a Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Method for Detection of Certain bla KPC -Containing Plasmids

“…Since nonoptimized performance of a part (or parts) within an instrument can significantly impact the sensitivity of assays, especially those that solely detect a single spectral peak, it is conceivable that negative effects may also be seen for other tests such as antibiotic hydrolysis assays that detect small shifts in antibiotic mass (5-7). The effect on these assays may be especially important because the drug products are small and below the normal acquisition range of the Bruker MicroFlex LT MALDI-TOF mass spectrometer (5)(6)(7). Increasing use of MALDI-TOF MS assays that are sensitive to shifts in drug or protein mass or of those that rely solely on detection of a single peak in the clinical laboratory will provide insight into how common this issue is and help us better understand its potential impact on clinical diagnostics in the broader setting.…”

The Clinical Impact of Rapid, Direct MALDI-ToF Identification of Bacteria from Positive Blood Cultures

“…coli , organism identification alone is less helpful for informing antimicrobial agent choice. However, advances in the use of MALDI-ToF for generating susceptibility profiles [12–14] suggests that utilisation of the mass spectrometry technology is only set to increase. Rapid detection of organisms with highly resistant susceptibility profiles, such as carbapenemase producing enterobacteriaceae (CPE), would not only facilitate more appropriate antimicrobial choice but also give MALDI-ToF a vital role in hospital based infection prevention and control.…”

The Rapid Detection of Cefotaxime-Resistant Enterobacteriaceae by HPLC

“…Following a 1–2.5-h coincubation of gram-negative bacteria with a relevant antibiotic the ratio of hydrolyzed to nonhydrolyzed β-lactam could be used to classify resistance or susceptibility [27,33]. While MALDI-ToF MS is readily available in clinical microbiology laboratories, the mass of antibiotics and their hydrolysis products is below the normal detection range of the system and MALDI-ToF MS has limited capability to quantify molecules of low molecular mass (<1000 Da), which may reduce the sensitivity and accuracy of this approach [34,35].…”