J Clin Microbiol. 2021 Jul 7:JCM0123021. doi: 10.1128/JCM.01230-21. Online ahead of print.
The global incidence of mucormycosis has increased in recent years owing to higher numbers of individuals at risk for these infections. The diagnosis and treatment of this aggressive fungal infection are of clinical concern due to differences in species distribution in different geographic areas and susceptibility profiles between different species that are capable of causing highly aggressive infections. The purpose of this study was to evaluate the epidemiology and susceptibility profiles of Mucorales isolates in the U.S. over a 52-month period. Species identification was performed by combined phenotypic characteristics and DNA sequence analysis, and antifungal susceptibility testing was performed by CLSI M38 broth microdilution for amphotericin B, isavuconazole, itraconazole, and posaconazole. During this time-frame, 854 isolates were included, representing 11 different genera and over 26 species, of which Rhizopus (58.6%) was the predominant genus followed by Mucor (19.6%). The majority of isolates were cultured from the upper and lower respiratory tracts (55%). Amphotericin B demonstrated the most potent in vitro activity, with GM MICs of ≤0.25 μg/mL against all genera with the exception of Cunninghamella species (GM MIC 1.30 μg/mL). In head-to-head comparisons the most active azole was posaconazole followed by isavuconazole. Differences in azole and amphotericin B susceptibility patterns were observed between the genera with the greatest variability observed with isavuconazole. Awareness of the epidemiology of Mucorales isolates and differences in antifungal susceptibility patterns in the U.S. may aide clinicians in choosing antifungal treatment regimens. Further studies are warranted to correlate these findings with clinical outcomes.