Antifungal Susceptibility in Serum and Virulence Determinants of Candida Bloodstream Isolates from Hong Kong

Abstract

Candida bloodstream infections (CBI) are one of the most common nosocomial infections globally, and they account for a high mortality rate. The increasing global prevalence of drug-resistant Candida strains has also been posing a challenge to clinicians. In this study, we comprehensively evaluated the biofilm formation and production of hemolysin and proteinase of 63 CBI isolates derived from a hospital setting in Hong Kong as well as their antifungal susceptibility both in the presence and in the absence of human serum, using standard methodology. Candida albicans was the predominant species among the 63 CBI isolates collected, and non-albicans Candida species accounted for approximately one third of the isolates (36.5%). Of them, Candida tropicalis was the most common non-albicans Candida species. A high proportion (31.7%) of the CBI isolates (40% of C. albicans isolates, 10% of C. tropicalis isolates, 11% of C. parapsilosis isolates, and 100% of C. glabrata isolates) were found to be resistant to fluconazole. One of the isolates (C. tropicalis) was resistant to amphotericin B. A rising prevalence of drug-resistance CBI isolates in Hong Kong was observed with reference to a previous study. Notably, all non-albicans Candida species, showed increased hemolytic activity relative to C. albicans, whilst C. albicans, C. tropicalis, and C. parapsilosis exhibited proteinase activities. Majority of the isolates were capable of forming mature biofilms. Interestingly, the presence of serum distorted the yeast sensitivity to fluconazole, but not amphotericin B. Taken together, our findings demonstrate that CBI isolates of Candida have the potential to express to varying extent their virulence attributes (e.g., biofilm formation, hemolysin production, and proteinase activity) and these, together with perturbations in their antifungal sensitivity in the presence of serum, may contribute to treatment complication in candidemia. The effect of serum on antifungal activity warrants further investigations, as it has direct clinical relevance to the treatment outcome in subjects with candidemia.

Anticandidal effect of endophytic bacteria isolated from Equisetum arvense L. against Candida albicans and Candida glabrata

“…In human Candida can cause life threatening systemic infections 49 . Moreover, clinicians have been challenged by the failure of standard antifungal agents.…”

Evaluation of Antifungal Efficacy of Three New Cyclic Lipopeptides of the Class Bacillomycin from Bacillus subtilis RLID 12.1

“…In our study, we observed the geometric mean MIC (MIC g ) of 3.48 g/ml for AF 4 against the clinical isolates of C. auris (Table 1), a concentration at which negligible hemolysis was observed. In a recent study from Hong Kong, an alarming rise in resistance has been noted, with 40% of C. albicans, 10% of C. tropicalis, 11.1% of C. parapsilosis, and 100% of C. glabrata strains reported as fluconazole resistant (14). In the present study, fluconazole-resistant C. albicans (n ϭ 1), C. parapsilosis (n ϭ 1), and C. krusei (n ϭ 4) strains displayed MICs of 4, 8, and 4 g/ml, respectively, in the case of AF 4 (see Table S1 in the supplemental material).…”

An Update on Candida tropicalis Based on Basic and Clinical Approaches

“…C. tropicalis has also been considered a strong biofilm producer species and is highly adherent to epithelial and endothelial cells (Marcos-Zambrano et al, 2014 ). In addition, several recent investigations have reported the recovery of C. tropicalis resistant to the antifungal drugs currently available, such as the azoles derivatives, amphotericin B, and echinocandins (Choi et al, 2016 ; Seneviratne et al, 2016 ). In addition, C. tropicalis has been considered an osmotolerant microorganism and this ability to survive to high salt concentration may be important for fungal persistence in saline environments, contributing to the expression of virulence factors in vitro and resistance to antifungal drugs (Zuza-Alves et al, 2016 ).…”