P432 Detection of erg11 gene mutation in fluconazole resistant Candida albicans isolates
Authors: M.S. Sheena , Singh Rakesh 
Published: September 2022

Abstract

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PM

Objective
To determine the profile of fluconazole-resistant Candida isolates (FRCS) and the proportion of erg11 gene mutation in fluconazole-resistant C. albicans (FRCA) isolates

Methods
After getting approval from ethics the study was conducted on 150 isolates of FRCS obtained from patients admitted to our tertiary care hospital from September 2019 to December 2021. All the isolates were revived onto Sabouraud dextrose agar (SDA) and identified by Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS). Fluconazole-resistance was detected by VITEK 2 automated system. Deoxyribonucleic acid (DNA) of FRCA isolates were extracted by QIAamp DNA Mini kit (Qiagen-51 304, Hilden, Germany) as per manufacturer's instruction. A single primer pair targeting the nucleotide sequence from 1067 to 1576 bp region of erg11 gene was used for amplification as per Xu et al. with minor modification and 500 bp polymerase chain reaction (PCR) products were observed by gel electrophoresis. A positive clinical isolate of FRCA was used as a positive control. The PCR products were purified and subjected to Sanger sequencing with an ABI PRISM DNA analyzer (Applied Biosystems) and mutations were detected by using Mega (version 7) software by comparing with the published GenBank sequence AF153844.1 of C. albicans strain ATCC 28516. Categorical variables were expressed in percentages and continuous variables were expressed in mean (average).

Results
Out of the total of 150 FRCS, the most common fluconazole-resistant agent of candidiasis was C. auris, which was isolated from 60 (40%) cases followed by 24 (16%) isolates of C. glabrata, 19 (12.7%) isolates of C. krusei, 18 (12%) isolates of C. parapsilosis, 17 (11.3%) isolates of C. albicans, 10 (6.7%) isolates of C. tropicalis, and only two (1.3%) isolates of C. guilliermondii. Among these 17 FRCA isolates, 9 isolates were obtained from genital swabs, 5 from blood, and a single isolate each from the perianal swab, ear swab, and sputum. A total of 12 (70.6%) out of 17 FRCA isolates yielded 500 bp region in erg11 gene. Gel electrophoresis image of PCR products of erg11 gene is depicted in Figure 1. Sequencing of these products detected a single missense mutation A1309G (V437I) in one FRCA isolate. Most of the FRCA isolates had an average of 4 silent mutations (observed in 6 isolates) and a single isolate had 6 silent mutations. A total of 8 different silent mutations were observed among FRCA isolates T1296C (83.3%), C1203T (66.7%), A1440G (66.7%), C1302T (50%), T1470C (50%), T1140C (25%), T1110C (16.7%), and T1284C (8.3%).

Conclusion
C. auris was the most common fluconazole resistant isolate observed, followed by C. glabrata, C. krusei, C. parapsilosis, C. albicans, C. tropicalis, and C. guilliermondii. There were many silent mutations observed in erg11 gene of FRCA isolates and detected only a single missense mutation (V437I). Fluconazole-resistant in FRCA isolates may be due to mechanisms other than the studied one in our region.