Abstract
Prompt and targeted antifungal treatment has a positive impact on the clinical outcome of mucormycosis; however, current diagnostic tools used in histopathology laboratories often fail to provide rapid results. Rapid culture-based strategies for early diagnosis of Mucorales infections, which may influence treatment decisions, are urgently needed. Herein, we evaluated a microculture assay for the early diagnosis of mucormycosis in an immunocompetent murine model of disseminated infection, by comparing it with traditional diagnostic methods. The assay specificity was assessed using blood (n = 90) and tissue (n = 90) specimens obtained from mice infected with Rhizopus arrhizus using different inoculum sizes [1 × 104, 1 × 105, and 1 × 106 colony forming units (CFUs)/mouse] and blood (n = 15) and tissue specimens (n = 15) from uninfected mice. Surprisingly, 26 of 90 (28.9%) blood samples revealed positive results by microculture, whereas all blood samples were negative when assayed by conventional culture. The overall positive conventional culture rate for the mouse tissue (kidney) samples was 31.1% (28/90). The calculated sensitivity for kidney microculture was 98.8% [95% confidence interval (CI) 96.6–100], with an assay specificity of 100%. Hence, the microculture assay may be useful for rapid culturing and diagnosis of mucormycosis caused by R. arrhizus directly in blood and tissue samples. Hence, this method may allow for the timely administration of an appropriate treatment.
Highlights
Mucormycosis, an aggressive infection caused by mucoralean fungi, is the third most prevalent fungal disease after candidiasis and aspergillosis, among populations at high risk, including those with uncontrolled diabetes, solid organ or allogeneic stem cell transplant recipients, and patients undergoing immunosuppressive therapies (Petrikkos et al, 2012; Danion et al, 2015; Farmakiotis and Kontoyiannis, 2016; Hoenigl et al, 2018; Cornely et al, 2019)
Fungal burden was significantly higher in mice infected with 1 × 106 colony forming units (CFUs) compared to the other inocula levels in the 1 × 104 and 1 × 105 CFU/mouse groups (p < 0.001)
We present the results of a microculture assay for timely culture of R. arrhizus
Summary
Mucormycosis (previously called zygomycosis), an aggressive infection caused by mucoralean fungi, is the third most prevalent fungal disease after candidiasis and aspergillosis, among populations at high risk, including those with uncontrolled diabetes, solid organ or allogeneic stem cell transplant recipients, and patients undergoing immunosuppressive therapies (Petrikkos et al, 2012; Danion et al, 2015; Farmakiotis and Kontoyiannis, 2016; Hoenigl et al, 2018; Cornely et al, 2019). The current gold standard for diagnosing mucormycosis is based on histopathological and mycological findings, followed by unspecific radiological criteria. These procedures require specialized expertise and the results are often not available in a timely fashion (Hammond et al, 2011; Cornely et al, 2019). Despite our improved understanding of the disease and the availability of various medico-surgical treatments, the survival rate in mucormycosis patients remains poor (Kontoyiannis and Lewis, 2011; Katragkou et al, 2014; Pilmis et al, 2018; Skiada et al, 2018). Several new molecular methods for the diagnosis of mucormycosis have been reported (Hammond et al, 2011; Dadwal and Kontoyiannis, 2018); these techniques may lack sensitivity, can be time-consuming and expensive to perform, and are not universally available (Katragkou et al, 2014)
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