Özlem Abaci

Investigation of Extracellular Phospholipase and Proteinase Activities of Candida Species Isolated from Individuals Denture Wearers and Genotypic Distribution of Candida albicans Strains

In order to determine the relationship between the development of denture related stomatitis (DRS) and the production of phospholipase and proteinase by Candida species, 156 Candida isolates isolated from the individuals in the control group and from the individuals different denture wearers were included in this study. According to the results of the study, C. albicans strains were determined to produce high levels of phospholipase and proteinase. It was also determined that the prevalence of phospholipase and proteinase activities in C. albicans strains isolated from individuals with DRS and from the individuals without DRS was not different. In order to determine genotypic variation of 109 C. albicans strains isolated, CA-INT-L and CA-INT-R primers specific to the site of the transposable group I intron of the 25S rRNA gene (rDNA) region were used. As a result, it was considered that, there were several other virulence factors belonging to the microorganism which played a role in the development mechanisms of the infection caused by C. albicans. In addition, according to the results of microbial genotyping, it was determined that there were no C. albicans strains specifically responsible for the development of DRS.

Investigation of the susceptibility of Candida species isolated from denture wearers to different antifungal antibiotics

The aim of this study was to determine the the prevalence of in vitro resistance amongst Candida species isolated from the oral cavity of denture wearers. The in vitro susceptibility of 156 Candida isolates to amphotericin B, fluconazole, 5- fluorocytosine, caspofungin and terbinafine was determined. The Clinical Laboratory Standards Institute’ (CLSI; formally National Committee for Clinical Laboratory Standards) broth microdilution method was used and MIC50 and MIC90 determined. Candida albicans, the most frequently isolated strains, are sensitive to amphotericin (61%) and fluconazole (44%), frequently used agents in the treatment of Candida-associated denture stomatitis. A 100% susceptibility to 5-fluorocytosine was observed among the 109 isolates of C. albicans. Among non C. albicans strains only 1 Candida kefyr strain was determined as susceptible dependent upon dose for 5-fluorocytosine. Among Candida glabrata, the second most common isolate, a 100% susceptibility to caspofungin and 5-fluorocytosine were observed. Since the isolates are sensitive to Caspofungin and 5-fluorocytosine, rarely used in the treatment of oral fungal infections, it is suggested that these antifungal agents be used as alternative medicine in the treatment of oral infections especially caused by strains resistant to amphotericin B and fluconazole.

Molecular typing of Candida albicans strains isolated from denture wearers by repetitive sequence-based PCR

Long-term use of prosthesis is the most important risk factor for the colonization of Candida species on the mucosal surfaces, which can lead to the development of denture-related stomatitis (DRS). Some individuals wearing prosthesis develop DRS and others do not. C. albicans strains isolated from both groups were genotypically compared. The purpose of this study was to determine whether the strain causing prosthesis stomatitis was different from the other strains genotypically. The study included 90 individuals wearing different prostheses and 20 control individuals with natural teeth. In the study 109 C. albicans strains were used which were isolated from the saliva samples and the mucosal surfaces of the tongues and palates of 51 individuals and then defined phenotypically. Phenotypic diagnosis of the isolates was genotypically verified by using species-specific PCR. For molecular typing, repetitive extragenic palindromic sequence polymerase chain reaction (REP-PCR) was employed. The results of the study revealed that REP-PCR had the capability to separate 109 C. albicans strains and six reference strains into 44 genotypes. Whereas C. albicans strains showed heterogenic distribution, C. albicans strains isolated from the individuals suffering from prosthesis stomatitis showed no specific genotypes. REP-PCR is a simple, fast and low-cost method and helped work on a great number of samples.

Specific identification ofCandida albicans andCandida dubliniensis by PCR using species-specific primers

The aim of our study was to evaluate the effectiveness of phenotyping and genotyping methods for the identification ofCandida albicans andCandida dubliniensis. Phenotyping methods used are colony colour on CHROMagar Candida medium, growth at 45°C, TTC (2,3,5-triphenyl-tetrazolium chloride) reduction, germ tube and chlamydospores formation, and API 20C AUX. We also usedC. albicans andC. dubliniensis specific primers for identification performed with genotyping methods. DNAs ofC. albicans reference strains, differentCandida species,Cryptococcus neoformans, mycelial fungi, bacterial strains and human DNA were used as a template in order to evaluate the specificity of the primers. These primers yielded a 175-base-pair product only whenC. albicans DNA exists; however when other DNAs (except two isolates that are phenotypically identified asC. dubliniensis andC. tropicalis) exist no product appeared. In another PCR assay conducted by usingC. albicans DNA andC. dubliniensis specific primers, no product was observed.Candida albicans andC. dubliniensis specific primers were designed by Mannarelli and Kurtzman. Detection limit ofC. albicans primers was found to be 19 pg chromosomal DNA. In order to verify phenotypical definition with PCR amplification,C. albicans andC. dubliniensis specific primers were exposed to PCR by using DNAs that belong to 25 phenotypically defined oralCandida isolates.