BACKGROUND
Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) allows rapid pathogen identification and potentially can be used for antifungal susceptibility testing (AFST).
OBJECTIVES
We evaluated the performance of the MALDI-TOF MS in assessing azole susceptibility, with reduced incubation time, by comparing the results with the reference method Broth Microdilution.
METHODS
Resistant and susceptible strains of Candida (n = 15) were evaluated against fluconazole and Aspergillus (n = 15) against itraconazole and voriconazole. Strains were exposed to serial dilutions of the antifungals for 15 h. Microorganisms’ protein spectra against all drug concentrations were acquired and used to generate a composite correlation index (CCI) matrix. The comparison of autocorrelations and cross-correlations between spectra facilitated by CCI was used as a similarity parameter between them, enabling the inference of a minimum profile change concentration breakpoint. Results obtained with the different AFST methods were then compared.
FINDINGS
The overall agreement between methods was 91.11%. Full agreement (100%) was reached for Aspergillus against voriconazole and Candida against fluconazole, and 73.33% of agreement was obtained for Aspergillus against itraconazole.
MAIN CONCLUSIONS
This study demonstrates MALDI-TOF MS’ potential as a reliable and faster alternative for AFST. More studies are necessary for method optimisation and standardisation for clinical routine application.
Key words:
antifungal susceptibility testing; azoles; MALDI-TOF MS; composite correlation index; Candida; Aspergillus
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