Multidrug resistance of Candida albicans fungi

Candida albicans is one of microorganisms of physiological human flora. It is normally isolated from mucous membrane of gastrointestinal and respiratory tracks, mouth and skin. Unfortunately this species is prone to cause opportunistic infections that consists mainly of superficial, though often persistent, oral or vaginal candidiasis. Much more problematic, and dangerous are systemic infections, called candidemias. These are most commonly seen in patients with severe immunosuppression that is caused by diseases which decrease the function of the immune system, such as cancer or AIDS or by prolonged exposure to antibio- or chemotherapy. Unfortunately, in recent years an increase in resistance of C. albicans to known antifungal agents has been observed. Additionally some of isolates display resistance to more than one drug, so called multidrug resistance MDR, which basically renders our attempts to treat this kind of infection futile.

C. albicans can develop many different kinds of mechanisms of drug resistance, such as forming biofilms, changing composition of cell membrane or structure of drug transforming enzymes. Overexpression of MDR transporters, which actively export xenobiotics from cell, is only another example. In C. albicans three of these pumps were identified: CDR1, CDR2 (Candida drug resistance 1 and 2), which belong to ABC (ATP-biding cassettes) transporters family, that use energy from ATP hydrolysis and MDR1 from MFS family (Major Facilitator Superfamily), which use energy from proton transport across membrane.

In our laboratory we are investigating effects of various chemical compounds on activity of ABC transporters of C. albicans. Previously similar study of Saccharomyces cerevisiae species was conducted here in our lab [Krasowska et al., 2010]. The method with fluorescent dye can be used as antifungal agents in future.

 Isolation and characterization of biosurfactants

Biosurfactants, amphiphilic compounds, synthesized by microorganisms such as bacteria, and fungi have surface and antimicrobial properties. Microbial surfactants are in most cases low-molecular mass compounds such as lipopeptides, glycolipids, and phospholipids or high-molecular mass lipoproteins, lipopolysaccharides, proteins,polysaccharides and biopolymer complexes.  

In the Biotransformation laboratory isolated bacterial and yeast strains from fresh water and soil of Spitsbergen (Arctic) and identificated by 16S rRNA sequencing. Investigated microorganisms are psychotolerat strains, not grow at temperatures above 30^oC and have a broad spectrum of metabolic specificities e.g. a secretion of biosurfactants.

The arctic strain Pseudomonas fluorescens BD5 secreted the biosurfactant – pseudofactin –cyclic lipopeptide.  Pseudofactin II reduced the surface tension of water from 72 mN/m to 31.5 mN/m at a concentration of 72 mg/l. Its emulsification activity and stability was greater than that of the synthetic surfactants Tween 20 and Triton X-100. Moreover pseudofactin prevents adhesion and biofilms formation by uropathogenic bacteria and fungi on various surfaces (plastic, silicone and glass).