Diagnostic Performance and Clinical Utility of Conventional PCR Assay in Early Diagnosis of COVID-19 Associated Rhino-Orbito-Cerebral Mucormycosis

Abstract

Early diagnosis and treatment of rhino-orbital-cerebral mucormycosis (ROCM) are crucial. Potassium hydroxide with Calcofluorwhite (KOH + CFW) smears can demonstrate the fungal hyphae, but mixed infections caused by both mucorales and non-mucorales pose a diagnostic challenge. Polymerase chain reaction (PCR) can detect mixed infections and differentiate mucorales from non-mucorales. This study aimed to evaluate the utility of a single reaction PCR in the diagnosis of ROCM and the efficacy of nasal biopsy and endonasal swab in the detection of fungus. Sixty-six clinical samples were collected from 33 patients and were subjected to KOH + CFW smear, culture and PCR. PCR was performed using pan-fungal primers targeting the 28S large subunit rRNA gene, and the amplified products were further sequenced to identify the fungi. KOH + CFW smear, culture and PCR detected mucorales in 54.6%, 27.3% and 63.6% patients, respectively. PCR detected mixed infection in 51.5% patients compared to 9.1% by KOH + CFW smear. PCR detected fungus in 90% of nasal biopsies and 77.8% of endonasal swabs. Rhizopus spp. was the most common fungi identified in 43.2% of PCR-positive samples. PCR is effective in detecting mixed infection and in the diagnosis of ROCM. Nasal biopsies had better fungal detection rates than endonasal swabs.

Current Issues in Fungal Infections and COVID-19

“…Two studies in this Special Issue explore the usefulness of molecular techniques for the diagnosis of mucormycosis, especially in low-income areas. Mohapatra S et al [6] evaluate a pan-fungal PCR based on primers targeting the 28S large subunit rRNA gene, both in nasal swabs and surgical biopsies of suspected ROCM cases, confirming an earlier identification of the fungus and an increased sensitivity when added to fungal stains even in the case of performing only endonasal swabs. A PCR assay identified mixed infections in 17 of 33 (52%) patients, of which 6 (35%) were KOH + CFW negative and 7 (41.2%) were culture negative.…”