<p>Distribution of Pathogenic Yeasts in Different Clinical Samples: Their Identification, Antifungal Susceptibility Pattern, and Cell Invasion Assays</p>

Abstract

Introduction: Species of genus Candida are part of the common microbiota of humans; however, some of the Candida species are known opportunistic pathogens. Formation of biofilms, resistance to antifungal drugs, and increase in asymptomatic infections demands more studies on isolation, identification and characterization of Candida from clinical samples. Methods: The present manuscript deals with assessment of authentic yeast identification by three methods viz., DNA sequencing of 28S rRNA gene, protein profiles using MALDI-TOF MS, and colony coloration on chromogenic media. Antifungal susceptibility and in vitro cell invasion assays were performed to further characterize these isolates. Results: Comparison of three methods showed that DNA sequence analysis correctly identified more than 99.4% of the isolates up to species level as compared to 89% by MALDI-TOF MS. In this study, we isolated a total of 176 yeasts from clinical samples and preliminary morphological characters indicated that these yeast isolates belong to the genus Candida. The species distribution of isolates was as follows: 75 isolates of Candida albicans (42.61%), 50 of C. tropicalis (28.40%), 22 of C. glabrata (12.5%), 14 of C. parapsilosis (7.95%) and 4 of Clavispora lusitaniae (2.27%). Other species like Cyberlindnera fabianii, Issatchenkia orientalis, Kluyveromyces marxianus, Kodamaea ohmeri, Lodderomyces sp., and Trichosporon asahii were less than 2%. Antifungal susceptibility assay performed with 157 isolates showed that most of the isolates were resistant to the four azoles viz., clotrimazole, fluconazole, itraconazole, and ketoconazole, and the frequency of resistance was more in non-albicans Candida isolates. The susceptibility to azole drugs ranged from 7% to 48%, while 75% of the tested yeasts were susceptible to nystatin. Moreover, 88 isolates were also tested for their capacity to invade human cells using HeLa cells. In vitro invasion assay showed that most of the C. albicans isolates showed epithelial cell invasion as compared to isolates belonging to C. glabrata, C. parapsilosis and C. tropicalis. Discussion: The identification of yeasts of clinical origin by sequencing of 28S rRNA gene performed better than MALDI-TOF MS. The present study reiterates the world scenario wherein there is a shift from Candida strains to emerging opportunistic pathogens which were earlier regarded as environmental strains. The present study enlightens the current understanding of identification methods for clinical yeast isolates, increased antifungal drug resistance, epithelial cell invasion as a virulence factor, and diversity of yeasts in Indian clinical samples.

Anidulafungin Versus Micafungin in the Treatment of Candidemia in Adult Patients

“…The rate of fluconazole resistance against C. parapsilosis candidemia in our study was higher (59.1%) than those of previously reported studies (2–6%) [ 28 – 30 ]. Recently, the emergence of fluconazole resistance of C. parapsilosis from intensive care units (30–75%) has been reported [ 31 – 33 ].…”

Update of the list of QPS‐recommended biological agents intentionally added to food or feed as notified to EFSA 13: suitability of taxonomic units notified to EFSA until September 2020

“…Pote et al. (2020) compared three methods for yeast identifications, growth on chromogenic media, DNA sequencing of the 26S rRNA gene and protein profiles using MALDI‐TOF. The conclusion is that MALDI‐TOF is able to identify common species, but its effectiveness is limited for uncommon species of Candida, or members of uncommon genera.…”

Mitogenomics and mitochondrial gene phylogeny decipher the evolution of Saccharomycotina yeasts

“…For instance, the production of some of the most common products in human diet, like bread and wine, involves Saccharomyces cerevisiae (Botstein and Fink, 2011; Peter et al, 2018), while other yeasts contribute to the fermentation and flavoring of alcoholic beverages (Eldarov et al, 2016). Other members of the Saccharomycotina subphylum, like some Candida species, cause serious human infections (Wang et al, 2018; Pote et al, 2020). Besides their importance to humans, Saccharomycotina yeasts present several other characteristics, like single cell morphology, asexual reproduction by budding and sexual, by the formation of ascospores, as well as facultative respiration.…”