Abstract
Most Candida infections are related to microbial biofilms often formed by the association of different species. The objective of this study was to evaluate the interactions between Candida albicans and non-albicans species in biofilms formed in vitro. The non-albicans species studied were:Candida tropicalis, Candida glabrata and Candida krusei. Single and mixed biofilms (formed by clinical isolates of C. albicans and non-albicans species) were developed from standardized suspensions of each strain (10(7) cells/mL), on flat-bottom 96-well microtiter plates for 48 hour. These biofilms were analyzed by counting colony-forming units (CFU/mL) in Candida HiChrome agar and by determining cell viability, using the XTT 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide colorimetric assay. The results for both the CFU/mL count and the XTT colorimetric assay showed that all the species studied were capable of forming high levels of in vitro biofilm. The number of CFU/mL and the metabolic activity of C. albicans were reduced in mixed biofilms with non-albicans species, as compared with a single C. albicans biofilm. Among the species tested, C. krusei exerted the highest inhibitory action against C. albicans. In conclusion, C. albicans established antagonistic interactions with non-albicans Candida species in mixed biofilms.
Highlights
Yeasts of the Candida genus are opportunistic pathogens frequently encountered in humans, and can be isolated from 60% of the oral cavities of healthy adults.[1]
We demonstrated that C. albicans was able to establish competitive interactions with non-albicans species during biofilm formation and infection development processes in animal models
C. albicans grew to 6.24 log (CFU/mL), but the result was 0.40 log when it was grown in the mixed biofilm with C. krusei
Summary
Yeasts of the Candida genus are opportunistic pathogens frequently encountered in humans, and can be isolated from 60% of the oral cavities of healthy adults.[1]. C. glabrata can disseminate rapidly throughout the body, and infection caused by this species is associated with a high mortality rate.[5] C. tropicalis is another non-albicans species considered an important opportunistic pathogen. It is most frequently isolated from candidiasis, mainly in patients confined to intensive care units, and has been associated with fluconazole resistance.[6] C. krusei is an emerging pathogen, described as a systemic pathogen in patients with compromised host resistance, such as those with acquired immunodeficiency syndrome (AIDS).[7]
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