In-vitro susceptibility of Candida albicans and Candida stellatoidea to sulfamethoxazole

The susceptibility of organisms of the speciesCandida to sulfamethoxazole were tested in-vitro using the disc sensitivity method.Under specified conditions a zone of growth inhibition surrounding sulfamethoxazole tablet sensi disc was consistently produced in cultures ofCandida albicans, Candida stellatoidea andSaccharomyces cervisiae.Diameters of growth inhibition zone were measured and found to be greatest in cultures ofCandida stellatoidea andSaccharomyces, but growth inhibition inCandida albicans cultures was observed to a lesser degree.The correlation between in vivo pathogenicity of organisms of the speciesCandida, and degree of growth inhibition by sulfamethoxazole sensi disc presents an interesting relationship.     

Multilocus sequence typing confirms synonymy but highlights differences between Candida albicans and Candida stellatoidea

We used multi-locus sequence typing (MLST) to investigate 35 yeast isolates representing the two genome-sequenced strains plus the type strain of Candida albicans, four isolates originally identified as Candida stellatoidea type I and 28 representing type strains of other species now regarded as synonymous with C. albicans. DNA from all 32 C. albicans synonyms readily formed PCR products with the C. albicans MLST primer sets. Their sequences placed all of them within the existing C. albicans clade structure, represented by 1516 isolates. One isolate, originally received as Mycotorula sinensis, was resistant to flucytosine, but no other unusual susceptibilities were found to polyene, azole or echinocandin antifungal agents. The four isolates of C. stellatoidea type I coclustered with two other sucrose-negative isolates, originally identified as examples of Candida africana, in a group of strains highly distinct from the majority of C. albicans. Our results not only confirm the synonymity of all the isolates with C. albicans but also confirm an obvious genotypic difference in the case of C. stellatoidea type I.     

Efficient and rapid identification of Candida albicans allelic status using SNP-RFLP

Candida albicans is the most prevalent opportunistic fungal pathogen in the clinical setting, causing a wide spectrum of diseases ranging from superficial mucosal lesions to life-threatening deep-tissue infections. Recent studies provide strong evidence that C. albicans possesses an arsenal of genetic mechanisms promoting genome plasticity and that it uses these mechanisms under conditions of nutritional or antifungal drug stress. Two microarray-based methods, single nucleotide polymorphism (SNP) and comparative genome hybridization arrays, have been developed to study genome changes in C. albicans . However, array technologies can be relatively expensive and are not available to every laboratory. In addition, they often generate more data than needed to analyze specific genomic loci or regions. Here, we have developed a set of SNP-restriction fragment length polymorphism (RFLP) (or PCR-RFLP) markers, two per chromosome arm, for C. albicans . These markers can be used to rapidly and accurately detect large-scale changes in the C. albicans genome including loss of heterozygosity (LOH) at single loci, across chromosome arms or across whole chromosomes. Furthermore, skewed SNP-RFLP allelic ratios are indicative of trisomy at heterozygous loci. While less comprehensive than array-based approaches, we propose SNP-RFLP as an inexpensive, rapid, and reliable method to screen strains of interest for possible genome changes.     

A combination rapid and standard method for identification of Candida albicans

A medium consisting of an aqueous extract of zein, lactose, and Tween 80 is used together with an overlay of 1 % Tween 80 and coverslipping to provide a combined rapid (germ tube) and standard (chlamydospore) method for diagnosis ofCandida albicans. The method is exquisitely sensitive for diagnosis ofC. albicans but lumps chlamydospore-producing strains ofC. tropicalis withC. albicans.     

Utility of albicans ID plate for rapid identification of Candida albicans in clinical samples

Albicans ID (bioMérieux, Marcy l'Etoile, France) is a ready-to-use medium that contains a chromogenic substrate that allows rapid detection and specific identification of Candida albicans. We have evaluated its clinical performance by culturing 846 clinical specimens from pregnant women and neonates. A 99.2% sensitivity and a 100% specificity were observed in the identification of C. albicans isolates from primary culture.     

DNA homology between Candida albicans strains: Evidence to justify the synonymous status of C. stellatoidea

Genetic relatedness between strains of C. albicans and C. stellatoidea was studied by measuring G + C content and overall sequence homology. G + C contents determined by high-performance liquid chromatography were 32.6 to 34.2% for 26 strains of C. albicans and 33.0 to 33.9% for eight strains of C. stellatoidea. DNA-DNA hybridization with two C. albicans and two C. stellatoidea probes revealed that all 34 test strains formed a single cluster in which the extents of hybridization with the heterologous probes ranged between 77.9 and 105.6% of those with the homologous probes. These results give support to the unification of C. albicans and C. stellatoidea into a single species.     

A rapid screening test to distinguish between Candida albicans and Candida dubliniensis using NMR spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy combined with a statistical classification strategy (SCS) successfully distinguished between Candida albicans and Candida dubliniensis. 96% of the isolates from an independent test set were identified correctly. This proves that this rapid approach is a valuable method for the identification and chemotaxonomic characterisation of closely related taxa. Most discriminatory regions were correlated with metabolite profiles, indicating biochemical differences between the two species.     

Structure of the D-mannan of Candida stellatoidea IFO 1397 strain. Comparison with that of the phospho-D-mannan of Candida albicans NIH B-792 strain

The structure of the D-mannan of Candida stellatoidea IFO 1397 strain, which has properties identical to those of the phospho-D-mannan of C. albicans serotype B strain, does not contain phosphate groups, and its 1H- and 13C-n.m.r. spectra are quite similar to those of the phospho-D-mannan of C. albicans NIH B-792 strain. However, the 1H-n.m.r. and 1H-13C-correlation n.m.r. spectra of the products obtained by digestion with alpha-D-mannosidase of C. stellatoidea D-mannan considerably differed from those of the corresponding digestion products of the C. albicans phospho-D-mannan. Additionally, the enzyme-linked immunosorbent assay, by means of a monoclonal antibody corresponding to (1----2)-linked beta-D-oligomannosyl residues, of the phospho-D-mannan of the same C. albicans strain indicated that the C. stellatoidea D-mannan does not contain any (1----2)-linked beta-D-oligomannosyl residues. The absence of these residues may be used as one of the criteria of chemotaxonomical identification of C. stellatoidea spp.     

Interspecific hybridisation between Candida albicans and Candida tropicalis

Abstract Protoplasts from auxotrophic mutants of Candida albicans and Candida tropicalis were produced by snail enzyme treatment and their fusion was induced with polyethylene glycol (PEG). During selective regeneration, nutritionally complemented interspecific hybrids were obtained. Their cells contained one nucleus, and the DNA content per cell was higher than in the parents. The isoenzymic and sugar assimilation patterns of the mutants, and those of the hybrids and the products after their haploidisation, were also analysed. The results indicated that the hybrids were partial alloploids containing the total chromosomal set of either of the parental species and one or a few chromosomes of the other.     

Differentiation of Candida stellatoidea from C. albicans and C. tropicalis by temperature-dependent growth responses on defined media

C. stellatoidea differs from both C. albicans and C. tropicalis in its i) much greater growth differential on minimal and amino acid enriched media and ii) unique inability to grow on minimal medium containing glycerol as carbon source at 37C. The relative responses to amino acid enrichment occur on media containing either fermentative or oxidative carbon sources, at 25C or 37C. Under any given conditions of carbon source and temperature, different assortments of individual amino acids are stimulatory for each of the three species. All assortments include one or more members of the glutamic acid family. However, sulfur amino acids stimulate only C. stellatoidea on all three carbon sources. On minimal-glycerol medium, wild type strains of C. stellatoidea grow prototrophically at 25C but are auxotrophic for amino acids at 37C; the particular auxotrophies expressed vary from strain to strain. Slow growing, mycelial mutants, prototrophic on glycerol at 37C arise spontaneously in wild type strains at frequencies indicating nuclear gene mutation. Such mutants can be induced by both transition and frame shift mutagens. The implications of these observations for the taxonomic relationships between the three Candida species and for identification of C. stellatoidea in particular are discussed.     

白念珠菌SPE1基因高表达菌株构建及鉴定

目的构建白念珠菌SPEl基因高表达菌株。方法将白念珠菌．SPEl基因的ORF置于高表达质粒载体pCaE—xP的MErF3启动子后面,构建pCaEXP—SPEJ的高表达质粒,然后采用醋酸锂转染法将高表达质粒转染白念珠菌RMl000中,在SD—ura’met—cys-选择性固体培养基上筛选阳性克隆,抽取基因组进行PCR验证,将验证为阳性转染子的菌落采用RealTimeRT．PCR方法进行SPE1基因转录水平的表达验证。结果通过酶切鉴定pCaEXP—SPEl高表达质粒构建正确;通过PCR验证表明SPEl基因整合到亲本菌中的RPl0位点;通过RealTimeRT—PCR方法筛选出sPEJ基因在转录水平高表达的菌株。结论利用高表达质粒载体pCaEXP通过基因同源重组等方法正确构建SPEl基因高表达的白念珠菌。     

Simple new test for presumptive differentiation between genus Candida and genus Prototheca

A differential test was made between genus Candida and genus Prototheca using a new and very simple differential test.A total of 59 strains of Candida and 78 strains of Prototheca were used. The basis of the test was the differential use of a disc carrying 60 mcg of Rybostamicin to which all the Candida were resistant and the Prototheca inhibited.     

白念珠菌FLO8基因突变株构建及鉴定

目的构建白念珠菌FLO8基因突变株。方法将白念珠菌FLO8基因插入pCP20质粒载体ADH1启动子之后,通过定向诱变获得FLO8基因R209T、A311T、654Ter、G723R、T751D突变质粒载体,再通过同源重组技术将带有FLO8突变的基因片段整合至SN152flo8/flo8菌株的ADE2位点。结果通过测序鉴定FLO8基因突变质粒载体构建成功;通过PCR验证表明突变FLO8基因整合到SN152flo8/flo8菌株的ADE2位点。结论以pCP20质粒为载体,通过定向诱变、同源重组等技术,可以高效构建白念珠菌FLO8基因突变株。     

Antigenic relationship between Candida parapsilosis and Candida albicans serotype B

We examined the antigenic relationship between Candida parapsilosis and C. albicans serotype B with respect to antigenic factors 13 and 13b, specific for the former species and common to both species, respectively. Acetolysis of C. albicans serotype B cell-wall mannan gave six oligosaccharides. Their chemical structure was determined by 1H-nuclear magnetic resonance (NMR) spectroscopy, methylation analysis, and partial acid hydrolysis. The structure of the hexasaccharide derived from C. albicans serotype B mannan was alpha-D-Manp-(1-2)-alpha-D-Manp-(1-3)-alpha-D-Manp-(1- 2)-alpha-D-Manp-(1-2)- alpha-D-Manp-(1-2)-D-Man (M6) which is identical to that from C. parapsilosis mannan. Inhibition of two precipitin reaction systems (anti-C. albicans serotype B serum and anti-C. parapsilosis serum to the respective homologous mannan), by oligosaccharides from homologous and heterologous mannans indicated that M6 from either C. albicans serotype B or C. parapsilosis was the most effective inhibitor. Moreover inhibition of the agglutination reaction between factor serum containing anti-factors 13 and 13b and C. albicans serotype B or C. parapsilosis cells by oligosaccharides from both mannans also indicated that the M6s were the most effective inhibitors. These results suggest that the M6s derived from the two species are identical in their chemical structure, although the structures of the whole mannans of the two species are not identical as demonstrated by gel diffusion precipitation patterns, and that M6s may be involved in the specificities of antigenic factors 13 and 13b. The amount of M6 is larger in C. parapsilosis cell-wall mannan, suggesting that high repeating frequency of M6 fragment may induce the antibody specific for C. parapsilosis.