Abstract
Mass spectrometry by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) was used to identify and differentiate the pattern of susceptibility of clinical isolates of Candida parapsilosis complex. 17 C. parapsilosis sensu stricto, 2 C. orthopsilosis, and 1 C. metapsilosis strains were obtained from blood cultures, and three different inocula (103, 105, and 107 CFU/mL) were evaluated against three echinocandins at concentrations ranging from 0.03 to 16 µg/mL after incubation of 1 h, 2 h, and 3 h. Drug-free control was used. The spectra obtained at these concentrations were applied to generate composite correlation index (CCI) matrices for each yeast individually. After cross correlations and autocorrelations of each spectra with null (zero) and maximal (16) concentrations, the CCI was used as separation parameter among spectra. Incubation time and inoculum were critical factors to reach higher precision and reliability of this trial. With an incubation time of 3 h and inoculum of 107 CFU/mL, it was possible to determine the breakpoint of the clinical yeasts by MALDI-TOF that presented high agreement with the clinical laboratory standard institute (CLSI) reference method. Herein, we show that mass spectrometry using the MALDI-TOF technique is powerful when it exploits antifungal susceptibility testing assays.
Highlights
Incidence of invasive fungal infections (IFIs) has tragically increased during the last twenty years, despite advances in methods of diagnosis [1,2]
Among the 59 patients diagnosed with candidiasis, twenty were diagnosed as Candida parapsilosis complex by MALDI-TOF MS, and were selected for Antifungal Susceptibility Testing (AFST) by both microdilution method and mass spectrometry methodologies
The clinical laboratory standard institute (CLSI)-based AFST method showed that all 20 clinical isolates of Candida parapsilosis complex were susceptible against caspofungin and micafungin and one Candida parapsilosis sensu stricto was resistant against anidulafungin only
Summary
Incidence of invasive fungal infections (IFIs) has tragically increased during the last twenty years, despite advances in methods of diagnosis [1,2]. In a substantial number of cases, the diagnosis of candidemia is usually established late or even at autopsy [7]. In this sense, the general consensus assigns earlier initiation with precise antifungal treatments, proportionally increasing the patient survival. It is crucial to develop new rapid diagnostic methods capable of efficiently detecting IFIs at the beginning of the course of the disease, with high sensitivity and specificity [8]. The susceptibility profiles against antifungal drugs vary greatly between species, being necessary to the implementation of a rapid antifungal susceptibility test
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