Abstract
The development of rapid diagnostic assays for the identification and analysis of antimicrobial resistance of fungal pathogens causing invasive mycoses is of utmost importance to reduce morbidity and mortality. We evaluated the performance of a novel rapid procedure directly applied to monomicrobial blood cultures from patients with bloodstream infection caused by yeast species, including nine Candida and three non-Candida species. For the rapid procedure herein developed, samples of positive blood cultures were transferred into serum separator tubes and treated with sodium dodecyl sulfate; the yeast layer was recovered and directly used for microbial identification by MALDI-TOF mass spectrometry and antifungal susceptibility testing (AFST) by the Sensititre YeastOne Y010 panel. The results were compared with those obtained by the same methods applied to colonies isolated on solid media. Using a score value of 1.700 as cut-off for valid identification, the rapid procedure identified 66 of 124 (53.2%) isolates, all of which concordantly with the reference method. However, adopting a cut-off ≥1.300 and ≥4 consecutive repetitions of the same species in the list of matches would extend concordant identification to 107/124 (86.3%) samples. Importantly, AFST revealed essential agreement between the two methods for all the isolate/antifungal drug combinations tested, including misidentified and not identified isolates. Therefore, the procedure herein developed represents a valid alternative for AFST of yeasts from positive blood cultures, yielding accurate and reliable results at least 24 h earlier than with the routine procedure, thus allowing clinicians to promptly streamline antifungal therapy.
Highlights
Bloodstream infections (BSIs) are among the main causes of morbidity and mortality in hospitalized patients (Buehler et al, 2016)
66 of the 124 (53.2%) yeast strains were identified with score values ≥1.700
Eleven C. albicans and two C. parapsilosis were not identified and two yeasts were misidentified: one C. glabrata was misidentified as Candida krusei with score value 1.200 and two consecutive identical species ID in the list of matches, and one Candida orthopsilosis was misidentified as Candida lusitaniae with score value 1.130 and two consecutive identical species ID
Summary
Bloodstream infections (BSIs) are among the main causes of morbidity and mortality in hospitalized patients (Buehler et al, 2016) In this context, invasive Candida infections are associated with frequently unfavorable outcomes (Haltmeier et al, 2015) and mortality rates higher than 60% in critically ill patients (Kett et al, 2011; Guo et al, 2013; Barchiesi et al, 2014, 2017), especially when they are not timely and appropriately treated (Garey et al, 2006). The recent emergence of multidrug resistant (MDR) fungal pathogens (Lamoth et al, 2018), with varying susceptibility profiles to azole drugs, amphotericin B and echinocandins, poses a pressing need for rapid antifungal susceptibility testing (AFST)
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