Use of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry for Caspofungin Susceptibility Testing of Candida and Aspergillus Species

Abstract

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was evaluated for testing susceptibility to caspofungin of wild-type and fks mutant isolates of Candida and Aspergillus. Complete essential agreement was observed with the CLSI reference method, with categorical agreement for 94.1% of the Candida isolates tested. Thus, MALDI-TOF MS is a reliable and accurate method to detect fungal isolates with reduced caspofungin susceptibility.

Rapid Antifungal Susceptibility Testing by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Analysis

“…A panel of 65 C. albicans isolates with and without FKS1 gene (which encodes ␤-1,3-glucan synthase [GS], the echinocandin target) mutations that are known to be associated with resistance to CSF (25,26) were included in the study (see Table S1 in the supplemental material). Ten fks1 mutant isolates were previously investigated (19). Before testing, each isolate was subcultured onto Sabouraud dextrose agar to ensure its purity and viability and reidentified by standard methods.…”

“…Isolates were categorized as susceptible, intermediate, or resistant on the basis of the new CLSI breakpoints for CSF and C. albicans that were set at Յ0.25 g/ml (susceptible), 0.5 g/ml (intermediate), and Ն1 g/ml (resistant) (26). AFST by MALDI-TOF MS (ms-AFST) was performed according to our published method (19). Briefly, protein extracts were prepared from fungal isolates (starting from an inoculum of 1 ϫ 10 7 CFU/ml) grown in RPMI broth containing serial dilutions (ranging from 0.5 to 0.004 g/ml) or a breakpoint concentration (intermediate, 0.03 g/ml) of CSF (pure substance provided by Merck, Milan, Italy) at 37°C under agitation for 15 or 3 h, respectively.…”

“…Recently, we developed a MALDI-TOF MS-based assay for testing antifungal susceptibilities of clinically relevant Candida and Aspergillus species to the echinocandin caspofungin (CSF) (19) by means of a composite correlation index (CCI)-based approach (20). The method reliably and accurately allows a determination of the minimal profile change concentration (MPCC) (21), an endpoint value that is an alternative to the classical MIC, for CSF by relying on the proteome changes which are detectable after a 15-h exposure of fungal cells to serial drug concentrations (19).…”

“…Recently, we developed a MALDI-TOF MS-based assay for testing antifungal susceptibilities of clinically relevant Candida and Aspergillus species to the echinocandin caspofungin (CSF) (19) by means of a composite correlation index (CCI)-based approach (20). The method reliably and accurately allows a determination of the minimal profile change concentration (MPCC) (21), an endpoint value that is an alternative to the classical MIC, for CSF by relying on the proteome changes which are detectable after a 15-h exposure of fungal cells to serial drug concentrations (19). Endpoint readings by MALDI-TOF MS provide a clear time savings (15 h versus 24 h) over the CLSI-or EUCAST-based methods, but implementing MALDI-TOF MS into the daily workflow appears to offer only a subtle advantage to clinicians compared to that for recent strategies aimed at speeding up AFST (22,23).…”

Comparative Evaluation of the Bruker Biotyper and Vitek MS Matrix-Assisted Laser Desorption Ionization–Time Of Flight (MALDI-TOF) Mass Spectrometry Systems for Identification of Yeasts of Medical Importance

“…In particular, several studies have already demonstrated the reliability of MALDI-TOF MS in the rapid identification of yeasts in different clinical settings (5-7), evidencing its cost-effectiveness in allowing the initiation of species-targeted antifungal therapy (7)(8)(9). To date, four MALDI-TOF MS systems are commercially available: the Microflex LT Biotyper (Bruker Daltonics, Bremen, Germany) (BMS), the Saramis system (bio-Mérieux, Marcy l'Etoile, France), the Vitek MS system (bioMérieux, Marcy l'Etoile, France) (VMS), and, very recently, the Andromas system (Andromas, Paris, France).…”