Utility of nasal swabs as samples for the diagnosis of Mucormycosis using molecular methods for detection

ABSTRACT

Objectives: Mucormycosis is an aggressive, life-threatening infection caused by fungi in the order Mucorales. There was an explosion of new cases of rhino-sino-orbital mucormycosis following the COVID pandemic in India, and the need for easy and rapid diagnostics was felt. The current diagnosis of mucormycosis relies on mycological cultures, radiology, and histopathology. These methods lack sensitivity and are most definitive later in the course of infection, resulting in the failure of timely intervention. A real-time multiplex PCR platform is commercially available for the detection of Rhizopus spp., Mucor spp.Rhizomucor spp., Lichtheimia spp., and Cunninghamella spp. (PN-700, MucorGenius , PathoNostics , Maastricht, The Netherlands) This real-time PCR has been validated to identify these fungal pathogens from bronchoalveolar lavage, tissue, and serum samples. This study aimed to validate this PCR-based system to detect Mucorales from nasal swab samples and evaluate its utility in the detection of Mucorales from nasal cavities of high-risk patients developing signs and symptoms of mucormycosis. Method(s) A single-center cross-sectional observational study was conducted on 50 hospitalized adult patients with signs and symptoms of mucormycosis. Nasal swabs were taken for PCR analysis once there was a clinical suspicion and were com-pared with the results of the gold standard.The gold standard for the diagnosis of mucormycosis was the conventional method (KOHmountedmicroscopy/HPE).Demographicdetails andrisk factorsfor thesepatients wererecorded, andthe RTPCR-based test was run on the nasal swab samples of all these 50 patients. The workflow is depicted graphically in Fig. 1 (Created with BioRender.com). Result(s) The study population mean (SD) age was 50 (16) years and consisted of 32 (64%) males. A total of 39 (78%) patients were known cases of diabetes mellitus, 48 (96%) patients had amphotericin B intake, and 20 (40%) had posaconazole intake. In all, 21 (42%) patients had a past history of COVID-19 infection;14 patients had received steroids and 10 patients received oxygen support. PCR for Mucorales was positive in 15 (30%) patients while the KOH mount was positive in 4 (8%) patients. Conclusion(s) These results are not encouraging for the use of nasal swabs as the sample for diagnosis of mucormyco-sis. Though the PCR performed better on the swab samples than KOH preparation and culture techniques, it highlights the importance of using standard sampling methods.