Çeşitli klinik örneklerden izole edilen candida albicans suşlarının genotipik dağılımı
No Thumbnail Available
Files
Date
2004
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sosyal Bilimler Enstitüsü
Abstract
Genotypic Distribution of Clinical Isolates of Candida albicans With the emergence of more aggresive chemotherapy protocols to cancer patients and transplant recipients, and the increase in the number of AIDS patients and long term survival of these immunsuppressed patients, an increase in the number of fungal infections was observed, with Candida albicans as the leading etiological agent. Molecular typing of the infectious agent is especially important for epidemiological studies and for the development of appropriate infection control strategies. In this study, a total of 401 C. albicans isolates, 81 invasive (blood culture isolates) and 320 non-invasive (sputum, wound, urine, vagen, feaces and throat culture isolates), were genotyped according to the presence of the transposable group 1 mtron in the 25S rDNA gene according to the method developed by McCullough et al. (1999). The frequencies of genotypes A, B and C were found to be 51.9%, 65% and 31.9% respectively. Genotypes D and E which belong to C dubliniensis were not found. When the isolates were evaluated as invasive and non-invasive, the genotype frequencies were found as follows: Genotype: 65.4%-48.4%; Genotype B: 8.6%- 18.1%; Genotype C: 26%-33.4%. Statistically significant differences were observed between the isolation sites (p=0.07) and between invasive and non-invasive isolates (p=0.015), genotype A being more prevalent among invasive isolates and genotypes B and C being more prevalent among non-invasive isolates. When the groups were compared according to the presence of the group 1 intron, the differences became even more significant (p=0.001 and p=0.006 respectively). These results show that, this region can be important in determining invasiveness and the presence of group 1 intron may have an importance in determining invasiveness besides resistance to flucytosine. In this study, different subgroups with slightly different molecular wights were observed among genotype A isolates. These groups were identified by restriction endonuclease and sequence analayses and an easy differentiation scheme using HaeE and Mspl restriction andonucleases was made. As a result, 8 different subtypes (subtype a-»h) were identified among genotype A isolates and the sequences of these subtypes were submitted to the Genbank. Subtype a, which gives a 460bp PCR product, was found to carry the same sequence with the previously submitted sequence. The 46()bp subtype c and 459bp subtype e (which carries a lbp deletion), differed from subtype a with single base substitutions. The 478bp subtype b, h and h, and 468bp subtype d were found to carry some insertions among their sequences. Subtype f, which gives a PCR product of 447bp, was found to carry a 13bp deletion among with many single base substitutions. When the subtypes were evaluated according to their isolation sites and the hospitals which they were recovered; subtypes a, b, and c were found to account for 86.1% of the isolates, and recovered from various infection sites of the patients hospitalized in different hospitals. Subtype d was recovered only from blood cultures and this subtype accounted for 6.2% of all isolates, and 25% of blood culture isolates. This subtype may be important for its invasive nature Subtypes e and g were obtained from patients hospitalized in the same department and subtype h was isolated from only one patient. These three subtypes were thought to be strains causing infection in the same hospital department with microevalutionary changes As a result, the genotypic distribution of C. albicans isolates has a unique pattern in Turkey, the main difference being the high frequency of genotype C isolates. Among invasive isolates, genotype A was found to be significantly more prevalent; for this reason in determining the therapy protocols of patients with genotype A C. albicans as the ethnological agent, resistance to flucytocine and risk for invasiveness must be taken into consideration. In order to understand the role of different genotype A subtypes in different infection types and their importance in epidemiological studies, more sophisticated and large scale studies must be performed. Key Words : Candida albicans, DNA sequence analysis, Genotyping, PCR, Restriction endonuclease analysis.
Description
Keywords
Moleküler Tıp