Frequency of occurrence, seasonal variation and antifungal susceptibility of opportunistic Mucorales isolated from hospital soils in Iran

Background Mucorales are opportunistic pathogens that can cause life-threatening diseases predominantly in immunocompromised patients. Objectives This study aimed to investigate the frequency, seasonal variation and antifungal susceptibility of pathogenic Mucorales in the soil collected from seven hospitals in Urmia, Iran, between November 2017 and July 2018 in four different seasons. Methods Mucorales isolates obtained from soil were characterised based on conventional and molecular assays. In addition, in vitro antifungal susceptibility was performed using the CLSI M38Ed3 procedure. Results Out of 196 tested soil samples, 80 (40.8%) samples were positive for mucoralean fungi. Rhizopus arrhizus var. arrhizus (n = 47) was the most frequent species followed by Mucor circinelloides (n = 21) and Cunninghamella echinulata (n = 6). A seasonal variation in the frequency of Mucorales in soil was detected with a maximum of culture-positive soil samples detected in wet autumn (43.2%) followed by winter (23.4%), summer (19.7%) and spring (13.6%). In vitro antifungal susceptibility testing for 80 environmental isolates exhibited MIC of <= 2 mu g/ml for amphotericin B indicating the smallest range of MIC variation among the tested Mucorales (range: 0.125-2 mu g/ml). Among the azoles, posaconazole was the most effective antifungals (GM MIC, 0.724 mu g/ml). Conclusions We considered associations of species and seasonal frequencies between soil mucoralean fungi and mucormycosis. The effect of opportunistic Mucorales dominating in the soil and prevalent causative agents of mucormycosis in Iran reported in the literatures but more comprehensive studies are needed to confirm this conclusion.

Automated summary

This study investigated the frequency, seasonal variation, and antifungal susceptibility of pathogenic Mucorales in soil collected from seven hospitals in Urmia, Iran. The most common species found was Rhizopus arrhizus var. arrhizus, and the highest frequency of Mucorales in soil was detected in wet autumn. In vitro antifungal susceptibility testing showed amphotericin B and posaconazole to be effective against the tested Mucorales isolates.