Abstract
Candia tropicalis is an increasingly important human pathogen, causing nosocomial fungemia among patients with neutropenia or malignancy. However, limited research has been published concerning its pathogenicity. Based on the phenotypes of C. tropicalis in our previous study, we selected nine representative strains with different activities of virulence factors (adhesion, biofilm formation, secreted aspartic proteinases, and hemolysins), and one reference strain, ATCC750. The present study aimed to investigate the filamentation ability, the expression of virulence genes (ALST1-3, LIP1, LIP4, and SAPT1-4) and the cell damage of C. tropicalis strains with diverse virulences. C. tropicalis exhibited strain-dependent filamentation ability, which was positively correlated with biofilm formation. Reverse transcriptase PCR analysis showed that the ALST3 and SAPT3 genes had the highest expression in their corresponding genes for most C. tropicalis. The expressions of virulence genes, except ALST3 on polystyrene, were upregulated compared with growth in the planktonic and on human urinary bladder epithelial cell line (TCC-SUP) surface. Clustering analysis of virulence genes showed that isolates had a high biofilm forming ability on polystyrene formed a group. Lactate dehydrogenase assays showed that the cell damage induced by C. tropicalis markedly increased with longer infection time (24 and 48 h). Strain FXCT01, isolated from blood, caused the most serious cell damage; while ZRCT52, which had no filamentation ability, caused the least cell damage. Correlation analysis demonstrated significant correlation existed between adhesion on epithelial cells or the expression of ALST2-3 and cell damage. Overall, our results supported the view that adhesion and filamentation may play significant roles in the cell damage caused by C. tropicalis.
Highlights
Candida tropicalis, an emerging opportunistic pathogen, mainly causes superficial and invasive infections in human populations, especially among neutropenic patients and those with hematological malignancies (Guinea, 2014)
biofilm formation (BF) and hydrolytic enzymes for C. tropicalis indicated that all isolates could produce adhesion, BF, secreted aspartyl proteases (Saps), and hemolysins with strain-dependent features, while no phospholipases were detected (Yu et al, 2015)
Compared with C. albicans, relatively little is known about the virulence of C. tropicalis
Summary
An emerging opportunistic pathogen, mainly causes superficial and invasive infections in human populations, especially among neutropenic patients and those with hematological malignancies (Guinea, 2014). Several factors were reported to contribute to Candida pathogenicity, including adhesion to medical devices and host cells; biofilm formation (BF); filamentation ability; and secretion of hydrolytic. Candida tropicalis Virulence Activities enzymes, including secreted aspartyl proteases (Saps), esterases, lipases, phospholipases, and hemolysins (Silva et al, 2011b; Lackey et al, 2013; Hirakawa et al, 2015). Adherence to host cells is the first step in invasive infections by Candida and in the BF, which plays a vital role in its pathogenicity (Ramage et al, 2006; Silva-Dias et al, 2015). Hydrolytic enzymes might play an important role in infection by disrupting host mucosal membranes, degrading immunological and structural defense proteins, and providing nutrients (Buzzini and Martini, 2002; Silva et al, 2012; Rossoni et al, 2013). The specific gene sequences of SAPT1-4, LIP1, and LIP4 could be found in GenBank
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