McCullough M J, Clemons K V, Stevens D A
Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, and California Institute for Medical Research, San Jose, California 95128, USA.
J Clin Microbiol. 1999 Feb;37(2):417-21. doi: 10.1128/JCM.37.2.417-421.1999.
There have been increased reports of the isolation of unusual genotypic groups of Candida albicans (groups C and D) based on a well-defined genotypic method; this method uses cellular DNA digested with the EcoRI enzyme and the restriction fragment length polymorphisms (RFLPs) generated by agarose gel electrophoresis. The aim of the present study was to use additional molecular tools to characterize these unusual strains and to compare them with authentic strains of C. dubliniensis, a recently delineated species, and type I C. stellatoidea. The RFLPs of PCR products generated from the intergenic transcribed spacer (ITS) region did not differentiate among C. albicans genotypes A, B, and C and type I C. stellatoidea. However, this method did differentiate the C. albicans genotype D strains, which were identical to C. dubliniensis. The RFLPs generated by HaeIII digestion of the PCR products of the V3 region of the 25S rRNA gene (rDNA) could differentiate the same groups as RFLP analysis of the PCR amplicon of the ITS region. C. albicans genotype B isolates have been shown to have a transposable intron in the 25S rDNA, whereas genotype A isolates do not; C. dubliniensis strains also have an intron that is larger than that in genotype B C. albicans strains but that is in the same location. PCR designed to span this region resulted in a single product for C. albicans genotype A (450 bp), B (840 bp), type 1 C. stellatoidea (840 bp), and C. dubliniensis (1,080 bp), whereas the C. albicans genotype C isolates had two major products (450 and 840 bp). All C. albicans genotype D isolates gave a PCR product identical to that given by C. dubliniensis. These results indicate that those strains previously designated C. albicans genotype D are in fact C. dubliniensis, that no differences were found between type 1 C. stellatoidea and C. albicans genotype B strains, and that the C. albicans genotype C strains appear to have the transposable intron incompletely inserted throughout the ribosomal repeats in their genomes. The results of the antifungal susceptibility testing of 105 of these strains showed that, for fluconazole, strains of C. dubliniensis were significantly more susceptible than strains of each of the C. albicans genotypes (genotypes A, B, and C). The flucytosine susceptibility results indicated that strains of C. albicans genotype A were significantly less susceptible than either C. albicans genotype B or C. albicans genotype C strains. These results indicate that there is a correlation between the Candida groups and antifungal susceptibility.
基于一种明确的基因分型方法，白色念珠菌异常基因型组（C组和D组）分离的报告有所增加；该方法使用经EcoRI酶消化的细胞DNA以及琼脂糖凝胶电泳产生的限制性片段长度多态性（RFLP）。本研究的目的是使用其他分子工具来鉴定这些异常菌株，并将它们与都柏林念珠菌（一种最近划分出的菌种）的正宗菌株以及I型星状念珠菌进行比较。从基因间转录间隔区（ITS）区域产生的PCR产物的RFLP不能区分白色念珠菌A、B和C基因型以及I型星状念珠菌。然而，该方法确实区分了白色念珠菌D基因型菌株，这些菌株与都柏林念珠菌相同。由25S rRNA基因（rDNA）V3区域的PCR产物经HaeIII消化产生的RFLP能够区分与ITS区域PCR扩增子的RFLP分析相同的组。已表明白色念珠菌B基因型分离株在25S rDNA中有一个可移动内含子，而A基因型分离株则没有；都柏林念珠菌菌株也有一个内含子，其比白色念珠菌B基因型菌株中的内含子大，但位于相同位置。设计用于跨越该区域的PCR对白色念珠菌A基因型（450 bp）、B基因型（840 bp）、I型星状念珠菌（840 bp）和都柏林念珠菌（1080 bp）产生单一产物，而白色念珠菌C基因型分离株有两个主要产物（450和840 bp）。所有白色念珠菌D基因型分离株产生的PCR产物与都柏林念珠菌产生的相同。这些结果表明，那些先前被指定为白色念珠菌D基因型的菌株实际上是都柏林念珠菌，I型星状念珠菌和白色念珠菌B基因型菌株之间未发现差异，并且白色念珠菌C基因型菌株似乎在其基因组的核糖体重复序列中整个都有未完全插入的可移动内含子。对其中105株菌株进行的抗真菌药敏试验结果表明，对于氟康唑，都柏林念珠菌菌株比每种白色念珠菌基因型（A、B和C基因型）的菌株更敏感得多。氟胞嘧啶药敏结果表明，白色念珠菌A基因型菌株比白色念珠菌B基因型或白色念珠菌C基因型菌株的敏感性明显更低。这些结果表明念珠菌组与抗真菌药敏性之间存在相关性。
