| Objectives:Saccharomyces albicans is the main component of oral microflora, and also the most important opportunistic pathogen, which can cause endogenous infection from superficial to seriously deep-seated mycoses under the altered host conditions, such as the malignant cancer patients. Oral Candidiasis now becomes the main side-effect of anticancer chemotherapy. Anticancer treatment including chemotherapy or/and radiotherapy is still associated with several side effects. Among them, oral Candidiasis is one of the major source of illness, although strict oral hygienic care by using antifungal reagents to prevent them. Oral Candidiasis is often accompanied by pain, loss of taste, and reduction in intake, and weight loss. Thereby result in treatment delays and necessitate dose reduction. Furthermore some studies have shown its potential importance in the development of systemic candidiasis which would be vital for these patients. The main limitation of previously studies about oral Saccharomyces is the fact that only single isolate elected from each patient for each episode. In fact there is heterogeneity among the oral Saccharomyces population (all the Saccharomyces albicans colonies from the same patient) in phenotypic and genotypic aspects. Since there is great heterogeneity among the individuals of the oral Saccharomyces population, it is reasonable to believe that this randomly selected single isolate cannot represent the whole view of the oral Saccharomyces population. Until now, the heterogeneity in the oral Saccharomyces albicans population across China is still unknown, and many studies of genotype variation and antifungal resistance among isolates from AIDS patients have shown mixed results.The aim of this study was to to study the distribution and to identify heterogeneity of Saccharomyces albicans isolated from the population with cancer in China by using identification medium, subculture molecular typing, and antifungal susceptibility test. This may help us to understand the distribution,the antifungal drug susceptibility and genotypic characteristics of oral Saccharomyces isolated from cancer patients in China, and would assist in getting the accurate susceptibility test in clinical practice.Method:52 cancer patients receiving chemotherapy were sampled by oral mucosal swab, and the oral cheek mucosal specimens were cultured on CHROMagar CandidaTM plates for Candida identification.All the Saccharomyces albicans colonies on the plates were subcultured and genotypic grouped by PCR using primers reported to span a transposable intron region in the 25SrRNA gene, then submitted to antifungal drug susceptibility test with fluconazole and molecular typing by randomly amplified polymorphic DNA-PCR (RAPD) with primers RSD6 and RSD12.Results:Oral Saccharomyces strains were isolated from 28 of 52 patients and the frequency of oral Saccharomyces carriage of the cancer patients receiving chemotherapy is 53.85%(28/52), most of them are Saccharomyces albicans, the frequency is 48.08%(25/52). The frequency of oral Saccharomyces glabrata carriage is 5.77%(3/52).Genotypic subgroup A,B,C were determined, and genotypic group B is the predominant group,59.57%(112/188). More than 7 Saccharomyces albicans colonies were isolated from each of 12 patients (Group A), while less than 5 colonies were isolated from each of 16 patients (Group B). RSD6 and RSD12 were successful in eliciting 17(A1-A17) and 2 (B1-B2) genotypes, respectively from among the 188 isolates.The two primers were combined to generate 21 genotypes. The Saccharomyces albicans isolates obtained from the same patient and episode showed diversity for fluconazole revealed by MIC50 and MIC90. Conclusion:Saccharomyces albicans, especially genotypic subgroup B,rather than subgroup A, is the prevalence subpopulation in the oral Candida obtained from cancer patients receiving chemotherapy in China. And the heterogeneity in fluconazole susceptibility and genotypic of Saccharomyces albicans isolates can be detected. Furthemore, Saccharomyces albicans with varied fluconazole susceptibility and genotypic characteristics may coexist in the same oral Saccharomyces population. |
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