Selected Yeast Isolates Research Articles

In vitro susceptibility of clinical yeast isolates to fluconazole and terconazole

OBJECTIVE: Fifty clinical yeast isolates, representing equally Candida albicans, Candida krusei, Candida parapsilosis, Candida tropicalis, and Torulopsis glabrata, were tested in vitro for their susceptibility to terconazole and fluconazole. STUDY DESIGN: The minimal inhibitory concentrations of terconazole and fluconazole were determined by use of a proposed standardized broth macrodilution assay. Also, the response of selected yeast isolates to 25 μg of either drug was measured by agarose disk diffusion experiments. RESULTS: For all species the minimum inhibitory concentrations for terconazole were significantly lower than those for fluconazole ( p < 0.05). In fact, for each individual isolate the minimum inhibitory concentration of terconazole was consistently lower than that of fluconazole. Differences in the geometric mean of terconazole and fluconazole minimum inhibitory concentrations were largest among C. krusei and T. glabrata, followed by C. parapsilosis, C. tropicalis, and C. albicans, in order of decreasing difference. Disk diffusion experiments suggested that terconazole is a more effective fungistatic agent than fluconazole is. CONCLUSION: Terconazole may be more effective than fluconazole against yeast species other than C. albicans. (Am J Obstet Gynecol 1996;175:1626-31.)

Application of CHROMagar Candida for rapid screening of clinical specimens for Candida albicans, Candida tropicalis, Candida krusei, and Candida (Torulopsis) glabrata

CHROMagar Candida is a new differential culture medium that allows selective isolation of yeasts and simultaneously identifies colonies of Candida albicans, C. tropicalis, and C. krusei. We evaluated the use of this medium with 316 yeast isolates including 247 isolated directly on CHROMagar from clinical material. Over 95% of stock and clinical isolates of C. albicans, C. tropicalis, and C. krusei were correctly identified on the basis of colony morphology and pigmentation on CHROMagar. Additionally, CHROMagar also allowed the identification of C. (Torulopsis) glabrata at a similar level of accuracy. The overall agreement between two observers in reading the CHROMagar plates was 95%. Growth of Candida sp. isolates on CHROMagar had no adverse effect on antifungal MICs or Vitek identification results. In parallel, cultures of 548 stool and rectal swab specimens set up on CHROMagar and Sabouraud glucose agar (SGA) were positive in 234 instances. CHROMagar was positive and SGA was negative for 11 specimens, and CHROMagar was negative and SGA was positive for 18 specimens. A single yeast species was isolated on both media from 162 specimens, and in 146 (90%) of these specimens the same species was detected on both CHROMagar and SGA. A total of 43 of the 234 positive cultures contained mixtures of yeast species. Twenty (47%) of these mixed cultures were detected only on CHROMagar. CHROMagar is extremely useful in making a rapid presumptive identification of common yeast species. This capability plus the ability to detect mixed cultures of Candida spp. promises to improve and streamline the work flow in the mycology and clinical microbiology laboratory.

Utilization of Low Molecular Weight Lignin-Related Aromatic Compounds for the Selective Isolation of Yeasts: Rhodotorula vanillica, a New Basidiomycetous Yeast Species

Summary Low molecular weight lignin-related aromatic compounds were used as sole sources of carbon and energy for the selective isolation of yeasts. A total of 227 yeast strains were isolated from terrestrial and aquatic habitats and ascribed to three groups: ascomycetous yeasts (17.6%), ascomycetous yeast-like microorganisms (5.3%) and basidiomycetous yeasts (77.1%). About half of the strains, representing the proportions of the various groups, were identified to the species level. Among the basidiomycetous yeasts, those affiliated to the Ustilaginales were present in higher number (75 strains) than the representatives of the Tremellales/Filobasidiales (16 strains). The ability of each identified isolate to grow in liquid medium with the same composition as the solid selective isolation medium was checked. Only 41% of the ascomycetous yeasts were able to grow, whereas all the ascomycetous yeast-like isolates and 90% of the basidiomycetous yeasts had that capacity. A novel basidiomycetous anamorphic yeast species was found among the strains collected and is described as Rhodotorula vanillica . Conspecificity with the phenotypically similar species Rhodotorula ingeniosa was excluded based on absence of DNA-DNA complementarity.

Evaluation of Media for Selective Isolation of Yeasts from Oral, Rectal, and Burn Wound Specimens

Six media were evaluated to determine their ability to isolate yeasts and inhibit bacteria. The media included the following: Snyder, Snyder tellurite, Sabouraud tellurite, Littman-gentamicin, molybdate, and Mycosel (BBL). Doses of mixed intestinal gram-negative bacilli and enterococci were most effectively inhibited by Snyder tellurite agar. Klebsiella pneumoniae was the most common bacterial contaminant of the other media. All six media were comparable in isolating yeasts while preventing the growth of the oral bacterial flora. The selection of a basal fungal growth medium for tellurite incorporation to inhibit bacteria but permit growth of yeasts was affected by pH. The bacteriostatic effect of tellurite was decreased with increasing pH of media while fungistatic action was increased. The arbitrary selection of Snyder and Littman agars to isolate yeast from burn wound cultures demonstrated the need to include a selective medium for these specimens. Blood, phenylethyl alcohol blood agar, and Columbia CN blood agar were all inadequate for isolating yeasts from burns. Growth of a variety of filamentous saprophytic and pathogenic dimorphic fungi grew adequately on four of five selective media tested.

Selective media for yeasts and bacteria in apple juice and cider

AbstractFrom a large number of antibiotics and other inhibitory compounds surveyed in detail, several have been chosen for the selective isolation of yeasts and bacteria from the mixed microfloras of apple juices and ciders. Bacteria were isolated on a basal medium of apple juice plus yeast extract, in the presence of actidione and oxine, while a mixture of actinomycin and Aureomycin allowed the sole growth of yeasts. Diphenyl was also added to the medium for the suppression of moulds in samples heavily infected with these organisms.