P237 Molecular epidemiology of Cryptococcosis—over 14 years using Whole Genome Sequencing and Multi-Locus Sequence Typing

Abstract

Poster session 2, September 22, 2022, 12:30 PM - 1:30 PMObjectives Cryptococcus neoformans/Cryptococcus gatti causes Cryptococcosis—a systemic fungal disease in immunocompromised as well as immunocompetent individuals.Whole genome sequencing (WGS) technology provides insights into the molecular epidemiology of Cryptococcus species. The main objective of this study was to analyze the genetic variations between the Cryptococcal species isolated in our center from patients from different parts of India using WGS and Multi-Locus Sequence Typing (MLST).MethodsThis was a study done on 56 strains of Cryptococcus that had been previously identified as C. neoformans from patients who were treated at Christian Medical College from 2007-2020. The organisms were identified by conventional colony morphology and microscopy and species identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). To determine the genetic diversity of C. neoformans isolates and the genetic structures of their populations, these Cryptococcus species isolates were further subjected to whole genome sequencing (WGS) using the Illumina platform followed by MLST using seven different housekeeping genes for genotyping the isolates. Based on the analysis, the Cryptococcus species isolates were characterized into Molecular types and clonal types, and their prevalence calculated.ResultsIn this study out of the 56 Cryptococcal isolates, 50 were C. neoformans and 6 were C. gattii. A total of 46% of the patients from whom the Cryptococcus species were isolated from Eastern states of India and 42% were from South India. Out of the 50 C. neoformans 24 (48%) were isolated from patients infected with Human immunodeficiency virus (HIV), (14%) from those with autoimmune disorders, 6 (12%) from patients with post renal transplant on immunosuppressants. A total of 5/6 C. gatti patients were immunocompetent. The most common clinical presentation was meningoencephalitis with the CSF being the most common clinical sample from which the organism was isolated. The phylogenetic tree was constructed to identify the genetic similarities between the isolates. A total of 49/50 C. neoformans belonged to molecular type VNI (98%) and one was type VII (2%). They were also sub-typed into 11 sequence types including one novel sequence type (ST). A total of 44% of them belonged to the sequence type (ST) 93 followed by ST 5 (14%). WGS analysis of C. gattii is ongoing.ConclusionMolecular epidemiology of Cryptococcus species WGS and MLST is an important tool to understand the genetic diversity of Cryptococcus isolates in India over the years. Further studies on identifying the virulence factors and drug resistance mutations are needed to further understand the molecular mechanisms of disease pathogenesis.