Rapid Detection and Identification of Candidemia by Direct Blood Culturing on Solid Medium by Use of Lysis-Centrifugation Method Combined with Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry (MALDI-TOF MS)

Abstract

Candida sepsis is a life-threatening condition with increasing prevalence. In this study, direct blood culturing on solid medium using a lysis-centrifugation procedure enabled successful Candida species identification by matrix-assisted laser desorption-ionization time of flight mass spectrometry on average 3.8 h (Sabouraud agar) or 7.4 h (chocolate agar) before the positivity signal for control samples in Bactec mycosis-IC/F or Bactec Plus aerobic/F bottles, respectively. Direct culturing on solid medium accelerated candidemia diagnostics compared to that with automated broth-based systems.KEYWORDS Candida, candidemia, MALDI-TOF, blood culture, direct blood culturing, lysis-centrifugation, mass spectrometry, rapid tests, sepsis C andidemia is associated with a particularly high mortality rate that is increasing, especially among immunocompromised and critically ill patients (1-3). While early and appropriate treatment is vital (3), the slow growth of yeasts delays a timely diagnosis (4). The current diagnostic standard includes inoculation of the patient's blood into special bottles with liquid medium and incubation in an automated blood culture (BC) instrument (5). In cases where growth is detected, Gram staining is performed and the broth is subcultivated onto a solid medium to grow colonies for identification and antimicrobial susceptibility testing (AST) (4). The lysis-centrifugation blood culture (LC BC) method is an alternative approach, which has been available for decades but whose use has declined with the advent of blood culture automation (6-9). LC BC involves the selective lysis of blood cells with subsequent centrifugation and culturing of the sediment directly on agar plates (6). A recent study found that this approach provides a dramatic reduction in the time required for BC diagnostics of bacteria when combined with the modern methods of identification and susceptibility testing (10).In this study, we investigated whether the direct cultivation on solid medium using the LC BC method combined with identification by matrix-assisted laser desorptionionization time of flight mass spectrometry (MALDI-TOF MS) would result in a more rapid detection and differentiation of yeasts from blood compared to that with the currently used liquid medium-based automated BC instruments. We also investigated the impact of specific fungal or general media used with each method.

Intensive care medicine research agenda on invasive fungal infection in critically ill patients

“…New diagnostic tools with higher sensitivity and specificity are clearly needed. For the rapid diagnosis of Candida bloodstream infections, technologies such as MALDI-TOF allow the direct identification of bacteria from positive blood cultures whereas yeasts are poorly identified using this technique [76,77]. New technologies (i.e., fluorescence in situ hybridization) [78] capable of identifying Candida spp.…”

Direct Blood Culturing of Candida spp. on Solid Medium by a Rapid Enrichment Method with Magnetic Beads Coated with Recombinant Human Mannan-Binding Lectin

“…in 10 ml of whole blood, which is very close to the situation in the bloodstream in a majority of patients (30). Significantly, the M1 method took only 18 to 49 h to obtain individual colonies on solid medium, which reduced the time by (26,31,32), and they are more effective than other enrichment methods, such as hollow disk separation and lysis-centrifugation methods (33,34). Moreover, MBL has a broader spectrum of pathogen-capture ability than do other molecules such as antibodies and ApoH (35).…”

Evaluation of Identification and Susceptibility for Candida Spp. Isolated Directly from Positive Blood Culture Bottles

“…e ability to rapidly identify Candida species may be useful to promptly streamline the development of antifungal therapy based on empirical evidence [14,15]. However, the emergence and spread of fluconazole-resistant Candida have introduced a pressing need for rapid antifungal susceptibility tests [16].…”