Anidulafungin Susceptibility Testing of Candida glabrata Isolates from Blood Cultures by the MALDI Biotyper Antibiotic (Antifungal) Susceptibility Test Rapid Assay

Abstract

Echinocandins are the recommended first-line antifungals for treatment of invasive candidiasis. The increasing number of Candida glabrata strains resistant against echinocandins is an emerging health care concern. The rapid detection of resistant C. glabrata isolates is an urgent requirement for clinical laboratories. In this study, we developed the MALDI Biotyper antibiotic (antifungal) susceptibility test rapid assay (MBT ASTRA) for the rapid detection of anidulafungin-resistant C. glabrata isolates directly from positive blood cultures. Of 100 C. glabrata strains, MBT ASTRA classified 69 as susceptible and 29 as resistant. Microdilution assays performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, used as a standard reference, identified 65 susceptible, 9 intermediate, and 26 resistant isolates. Sequencing of hot spot 1 and hot spot 2 regions of the FKS1 and FKS2 genes classified 86 susceptible and 14 resistant isolates. The MBT ASTRA had sensitivity and specificity of 80% and 95%, respectively, compared to the microdilution method. Positive and negative agreement of MBT ASTRA was calculated at 100% and 80%, respectively, compared with the molecular sequencing approach. Together, these results revealed a high accuracy of MBT ASTRA compared to microdilution according to the CLSI and PCR analysis, resulting in a categorical agreement of 90% and 83%, respectively. The validity of MBT ASTRA was 98%. Importantly, MBT ASTRA provided antifungal susceptibility testing (AFST) within 6 h that was both accurate and reliable compared to the other two approaches, which require at least 24 h or are costly. Therefore, this method has the potential to facilitate clinical AFST rapidly at low sample costs for clinical labs already equipped with matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS).

Low level of antifungal resistance of Candida glabrata blood isolates in Turkey: Fluconazole minimum inhibitory concentration and FKS mutations can predict therapeutic failure

“…PCR amplification and sequencing of the PDR1 gene and HS1/2 regions of the FKS1/2 genes were performed as previously described 29,37 . Sequences were assembled and edited using SeqMan Pro software (DNASTAR) and aligned using MEGA 7.0 38 .…”

Drug-Resistant Fungi: An Emerging Challenge Threatening Our Limited Antifungal Armamentarium

“…Such analyses may provide results within a few hours, but various limitations (detailed in Section 5 ) may complicate interpretation [ 178 ]. Some MALDI-TOF MS assisted AFST methods have been evaluated for a limited number of fungal species and drugs [ 188 , 189 ]. The MALDI-TOF MS is promising but needs a simplified, automated method for testing a broad range of fungi and antifungals.…”

MALDI-TOF MS in a Medical Mycology Laboratory: On Stage and Backstage

“…under curve (AUC) displayed by the spectrum that can be correlated to the growth [71,72]. MBT-ASTRA sensitivity was higher than that of the spectrum changes method (96% vs. 85.3%), while the specificity was similar for both approaches (93.2% vs. 94.2%, respectively).…”

“…MBT-ASTRA also use the MALDI-TOF technology but it is quite different as it provides a semi-quantitative analysis of the strain growth inhibition (Table 1). It is based on analyzing the intensity of the peaks and areas under curve (AUC) displayed by the spectrum that can be correlated to the growth [71,72]. MBT-ASTRA sensitivity was higher than that of the spectrum changes method (96% vs. 85.3%), while the specificity was similar for both approaches (93.2% vs. 94.2%, respectively).…”