Identification of Mucorales in patients with proven invasive mucormycosis by polymerase chain reaction in tissue samples

BACKGROUND: Accurate diagnosis of mucormycosis, a life-threatening fungal infection, remains a challenge for physicians. OBJECTIVES: To identify the causative Mucorales in fresh clinical samples and formalin-fixed paraffin-embedded (FFPE) samples of patients with proven mucormycosis by molecular method. PATIENTS/METHODS: Fresh clinical samples of patients with proven mucormycosis according to the EORTC/MSG criteria admitted between 2015 and 2017 and histopathologically proven FFPE archives collected during 2004-2007 and 2015-2017 from Mazandaran University-affiliated hospitals of northern Iran were included. Seminested PCR targeting the 18S rDNA of Mucorales and ITS region was performed, and PCR products were then sequenced. RESULTS: While culture was positive only in 5 of 9 (56%) of fresh specimen cases, PCR was positive in all 9 (100%) histologically proven mucormycosis. Ten of 18 (56%) FFPE samples were PCR-positive. Overall, Mucorales PCR was positive in 19 of 27 (70%) samples. Mucorales species were Rhizopus arrhizus in 16 (84%) cases, R. arrhizus/Amylomyces rouxii in 2 (10.5%) cases and Rhizopus stolonifer in one case (5.5%). Among 27 mucormycosis cases, 25 (93%) cases were rhinocerebral, and 2 (7%) cases were disseminated. Diabetes mellitus (74%) and neutropaenia (63%) were the main risk factors. CONCLUSIONS: Seminested PCR targeting 18S rDNA region of Mucorales is useful for identification of the causative agents of mucormycosis.