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.