MALDI-TOF-MS for Rapid Detection of Fungi causing Mucormycosis during COVID-19 Pandemic from a Tertiary Care Hospital in Southern India: A Retrospective Cohort Study
Authors: Someshwaran R , Appalaraju B 
Published: September 2023

Introduction: Mucormycosis is an opportunistic fungal infection that became a public health emergency during the second wave of Coronavirus Disease-2019 (COVID-19). It is an acute, angioinvasive, opportunistic, and emerging mycosis caused by mucormycetes, resulting in a significantly fatal fungal infection among immunocompromised and/or immunosuppressed individuals. Mucormycosis has a specific predilection for blood vessels (angioinvasive) and tissues, leading to extensive necrosis and thromboembolic events. Globally, the incidence rate of mucormycosis varies from 0.005 to 1.7 per million people. Early diagnosis and appropriate therapy are crucial for clinical outcomes. Aim: To evaluate the mycological profile of mucormycosis during the COVID-19 pandemic using automated Matrix Assisted Laser Desorption Ionisation Time of Flight Mass Spectroscopy (MALDI-ToF-MS) in comparison with conventional fungal identification methods. Materials and Methods: A retrospective cohort study was conducted, collecting data from July 2020 to June 2022, involving 1,176 patients from various clinical departments who attended PSG Hospitals affiliated with PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India. Data analysis was performed from July 2022 to August 2022. Clinical specimens, including Bronchoalveolar Lavage (BAL), Sputum, Cerebrospinal Fluid (CSF), nasal swabs, tracheal aspirates, pus, blood, corneal scraping, eye discharge, and necrotised tissues, were subjected to Potassium Hydroxide (KOH) mount, conventional culture coupled with micrometry-aided microscopy, and MALDI-ToF-MS among suspected mucormycosis cases. The results were collected in Microsoft Excel, and data analysis was conducted using the International Business Machines Statistical Package for the Social Sciences statistical software (IBM SPSS) version 24.0. The study variables were expressed as descriptive statistics: frequency (N) and percentage (%). The incidence of mucormycosis, mycological profile, and diagnostic utility of conventional micrometry-aided microscopy-assisted culture were compared with the automated MALDI-ToF-MS protein signature method of testing. Results: Fungal elements were positive in 130 (11.05%) out of a total of 1,176 clinical samples, such as necrotised tissue, biopsy, and sputum, in the KOH mount. Fungal culture was positive in 258 (21.94%) out of 1176 samples, with mucormycosis detected in 73 (28.29%) of the culture-positive samples. The incidence of mucormycosis in this study was 73 (6.21%) out of 1176. A total of 101 (8.59%) samples showed positive results for mucormycetes through KOH, culture, and MALDI-ToF-MS. MALDI-ToF-MS could rapidly and specifically identify and confirm the causative agents of mucormycosis at their genus and species levels compared to KOH or culture. Conclusion: Simple, low-cost, and less laborious conventional culture coupled with micrometry-aided microscopy can detect Mucorales at the species level, where KOH microscopy could not differentiate between species. MALDI-ToF-MS can be employed for the rapid detection and confirmation of mucormycosis agents at the genus or species level