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F C Odds

Publications and source records attributed to F C Odds.

At least 55 records · Page 3Linked to original sources
PubMed1997

Multicenter evaluation of proposed standardized procedure for antifungal susceptibility testing of filamentous fungi.

A multicenter study was conducted to expand the generation and analysis of data that supports the proposal of a reference method for the antifungal susceptibility testing of filamentous fungi. Broth microdilution MICs of amphotericin B and itraconazole were determined in 11 centers against 30 coded duplicate pairs of Aspergillus spp., Fusarium spp., Pseudallescheria boydii, and Rhizopus arrhizus. The effect of inoculum density (approximately 10(3) and 10(4) CFU/ml), incubation time (24, 48, and 72 h), and procedure of MIC determination (conventional and colorimetric [Alamar Blue] evaluation of growth inhibition) on intra- and interlaboratory agreement was analyzed. Based on intra- (97 to 100%) and interlaboratory (94 to 95%) agreement for both drugs, the overall optimal testing conditions identified were determination of colorimetric MICs after 48 to 72 h of incubation with an inoculum density of approximately 10(4) CFU/ml. These testing conditions are proposed as guidelines for a reference broth microdilution method.

Antifungal Agents↗
PubMed1997

Candida and Torulopsis: a blinded evaluation of use of pseudohypha formation as basis for identification of medically important yeasts.

Seventy yeast isolates representing species in the genera Candida and Torulopsis but excluding Candida albicans were examined in three laboratories for production of pseudohyphae in Dalmau cultures. The microscopic morphology of the isolates was scrutinized by four individuals experienced in yeast identification and three inexperienced persons, all of whom were blinded as to the putative identification of the yeasts. For 49 (70%) of the 70 isolates, the seven observers recorded comparable scores for morphology, but 5 (7%) of the isolates showed extreme variation in recorded morphologies, from true hyphae formed to no pseudohyphae formed. Isolates of Candida parapsilosis and Torulopsis glabrata consistently did and did not form pseudohyphae, respectively: however, other Candida and Torulopsis spp. did not always express their expected morphologies. In 48 (19%) of 252 readings (seven observers), 36 isolates of Candida spp. were scored as forming no pseudohyphae, and in 22 (9.2%) of 238 readings, 34 isolates of Torulopsis spp. were recorded as forming true hyphae or pseudohyphae. These results show that pseudohypha formation is not a reliable characteristic for identification of yeasts at the genus level; we suggest that the merger of Torulopsis spp. into the genus Candida should be finally accepted.

Candida↗
PubMed1997

Mycology in oral pathology.

Candida species are responsible for all but exceptional examples of oral fungal infection. Oral Candida lesions are seen only in patients who are predisposed to such disease by physiological or immunological abnormalities, particularly by extremes of age and HIV infections. The infections can be acute or chronic, pseudomembranous ("thrush") or atrophic (erythemateous). In the AIDS patient, mixtures of clinical types may be seen. Diagnosis of oral Candida infection requires microscopic or culture proof of the involvement of a Candida species. Treatment depends on the type of patient and the type of infection. Topical antifungal agents, usually of the imidazole, triazole or polyene type, are commonly used, although non-specific antiseptics are recommended for denture cleansing in cases of denture-associated stomatitis.

AIDS-Related Opportunistic Infections↗
PubMed1996

Chitinase levels in guinea pig blood are increased after systemic infection with Aspergillus fumigatus.

The presence of chitinase activity in human serum has recently been described by us. On that occasion we speculated on the possible role of mammalian chitinases as a defense mechanism against chitin-containing pathogens. The results of the present study substantiate our hypothesis. We demonstrate and partially characterize the chitinase activities that are present in plasma of guinea pigs and in homogenates of A.fumigatus with the aid of the substrates MU-[GlcNAc]2,3 and also with glycol [3H]chitin. Upon infection with A.fumigatus the serum chitinase activity levels in the circulation of pathogen-free guinea pigs increased in a time-dependent manner. The increase was also dependent on the size of the infecting fungal inoculum. Antifungal treatment diminished the increases. The increased chitinase activity was of guinea pig origin. The activity of beta-hexosaminidase showed a very slight increase subsequent to the infection. The activities of three other enzymes of lysosomal origin (alpha-mannosidase, beta-galactosidase and beta-glucosidase) did not increase.

Animals↗
PubMed1996

Susceptibilities of Candida spp. to antifungal agents visualized by two-dimensional scatterplots of relative growth.

The growth of 811 clinical yeast isolates in the presence of single concentrations of antifungal agents was measured spectrophotometrically and expressed as a percentage of growth in inhibitor-free control cultures. Two-dimensional scatterplots of the relative growth data allowed for the simple visual determination of some susceptibility trends, including correlations in relative growth between different agents and in relative susceptibilities between different yeast species. A positive susceptibility correlation was found for relative growth results with the azole antifungal agents fluconazole, itraconazole, and ketoconazole for 504 Candida albicans isolates. The relative growth scatterplots for fluconazole versus itraconazole showed that 50 (9.9%) of 504 C. albicans isolates were outliers with respect to the 95% confidence limits for a line of correlated relative growth established with an initial test panel of 59 isolates of this species. The outlying isolates were relatively less susceptible to fluconazole than to itraconazole under the conditions of the test. Most of the outliers were received in 1993 and 1994; only 3.9% of the isolates received in 1991 and 1992 and 1.7% of the isolates received before 1991 showed this differential susceptibility. In addition, most of the outliers came from patients with human immunodeficiency virus infections. The relative growth scatterplots confirmed the known high susceptibility of most Candida parapsilosis isolates to both fluconazole and itraconazole and the specifically low susceptibility of Candida krusei isolates to fluconazole. The scatterplots also illustrated a tendency towards lower (and correlative) relative growth among oral isolates obtained from AIDS patients who responded to azole antifungal treatment than among isolates from clinical nonresponders.

AIDS-Related Opportunistic Infections↗
PubMed1996

Quality control guidelines for National Committee for Clinical Laboratory Standards--recommended broth macrodilution testing of ketoconazole and itraconazole.

Ketoconazole and itraconazole were tested in a multilaboratory study to establish quality control (QC) guidelines for yeast antifungal susceptibility testing. Two isolates that had been previously identified as QC isolates for amphotericin B, fluconazole, and flucytosine (Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258) were tested in accordance with the National Committee for Clinical Laboratory Standards M27-P guidelines. Each isolate was tested 20 times with the two antifungal agents in the five laboratories by using a lot of RPMI 1640 unique to each laboratory as well as a lot common to all five laboratories, thus generating 200 MICs per drug per organism. Overall, 96 to 99% of the MICs for each drug fell within the desired 3-log2 dilution range (mode +/- 1 log2 dilution). By using these data, 3-log2 dilution QC ranges encompassing 98% of the observed MICs for three of the organism-drug combinations and 94% of the observed MICs for the fourth combination were established. These QC ranges are 0.064 to 0.25 micrograms/ml for both ketoconazole and itraconazole against C. parapsilosis ATCC 22019 and 0.125 to 0.5 micrograms/ml for both ketoconazole and itraconazole against C. krusei ATCC 6258.

Antifungal Agents↗
PubMed1996

Multisite reproducibility of the Etest MIC method for antifungal susceptibility testing of yeast isolates.

A multicenter study was performed to establish the interlaboratory reproducibility of Etest, to provide an additional comparison of Etest MICs with reference broth macrodilution MICs, and to develop some tentative quality control (QC) guidelines for using Etest for antifungal susceptibility testing of Candida spp. Two QC strains, Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258, were tested by Etest against amphotericin B, fluconazole, flucytosine, itraconazole, and ketoconazole in each of four laboratories. The QC strains were tested 20 times each against the five antifungal agents by using a common lot of RPMI agar. A total of 80 MICs per drug per strain were generated during the study. Overall, 98 to 100% of the MICs fell within a 3 log2 dilution range for the respective yeast-antifungal agent combinations. The level of agreement of Etest MICs with broth macrodilution MICs was 86 to 100% with amphotericin B (C. krusei and C. parapsilosis), itraconazole (C. krusei and C. parapsilosis), flucytosine (C. parapsilosis), and fluconazole (C. parapsilosis). A lower level of agreement was observed with ketoconazole (C. krusei and C. parapsilosis). Although all participants reported identical Etest MICs, the MICs of flucytosine and fluconazole when tested against C. krusei fell well above the upper limits of the reference range for this strain. The tentative QC limits for the two QC strains and five antifungal agents when tested by the Etest methodology are the same as the QC limits when tested by the reference broth macrodilution method for amphotericin B and C. krusei, itraconazole and C. krusei, flucytosine and C. parapsilosis, fluconazole and C. parapsilosis, and itraconazole and C. parapsilosis. The Etest QC ranges are 1 dilution broader (4-dilution range) than the reference macrodilution method QC ranges for ketoconazole and C. krusei, amphotericin B and C. parapsilosis, and ketoconazole and C. parapsilosis.

Amphotericin B↗
PubMed1995

Antifungal susceptibility testing of yeasts: evaluation of technical variables for test automation.

The technical parameters for antifungal susceptibility testing with Candida species were reexamined to determine the optimal conditions for testing with semiautomated preparations of broth microdilution cultures, automated spectrophotometric readings of the cultures, and dose-response and endpoint determinations by means of a computer spreadsheet. Tests were based on proposed standard method M27P of the National Committee for Clinical Laboratory Standards for antifungal agents. RPMI 1640 broth with extra glucose to a final concentration of 2% gave higher and more reproducible drug-free control readings without affecting susceptibility endpoint readings. An inoculum of 8 x 10(4) yeasts per ml prepared from a carbon-limiting broth culture without further standardization was found to give optimal control readings after 48 h of incubation at 37 degrees C. For flucytosine, fluconazole, itraconazole, and ketoconazole, endpoints based on 50% growth inhibition (50% inhibitory concentration) gave the minimum variation with inoculum size and the fewest endpoint differences with RPMI 1640 medium obtained from two different suppliers. The 50% inhibitory concentration was also the optimal endpoint for fluconazole and ketoconazole susceptibilities in comparison with broth macrodilution MICs determined by the method of the National Committee for Clinical Laboratory Standards. Intralaboratory reproducibility was determined by retrospective analysis of replicate results for isolates retested at random over a 2-year period. This approach showed less favorable reproducibility than has been reported from purpose-designed, prospective antifungal susceptibility studies, but it may better reflect real-life test reproducibility. Susceptibility data for 616 clinical isolates of yeasts, representing 16 Candida and Saccharomyces spp., confirmed the tendency of Candida lusitaniae isolates to show relatively low susceptibilities to amphotericin B, the tendency of Candida krusei isolates to show low flucytosine and fluconazole susceptibilities, and the presence of some isolates in the species Candida albicans, Candida glabrata, and Candida tropicalis with low susceptibilities to azole derivative antifungal agents. The study demonstrates the value of automation and standardization in all stages of yeast susceptibility testing, from plate preparation to data analysis.

Antifungal Agents↗
PubMed1995

Oxygen as limiting nutrient for growth of Cryptococcus neoformans.

In microbroth cultures with RPMI 1640 medium, the growth yield of seven Cryptococcus neoformans isolates was unaffected by augmentation of the normal (0.2%) glucose concentration in the medium to 2%, and the addition of other potential carbon, nitrogen, and vitamin sources to the medium also failed to produce large changes in growth yield. However, macrobroth cultures of C. neoformans in RPMI 1640 that were agitated by rotation in air gave turbidities 6 to 37 times greater than those in identical cultures incubated statically, and similar levels of increase were seen whether the medium contained 0.2 or 2% glucose. Incubation of microplates under an oxygen atmosphere or with agitation by rotation led to an increase of up to twofold in growth turbidity of the yeast. The maximum increase was achieved by incubation with rotation and was dependent on the brand of microplate used. The findings implicate oxygen as a growth-limiting nutrient for C. neoformans. Incubation of microbroth cultures under conditions that enhance oxygen availability for antifungal susceptibility testing purposes may increase the speed of such tests and enhance the determination of MIC endpoints.

Antifungal Agents↗
PubMed1994

Molecular mechanisms of drug resistance in fungi.

Failures of treatment in fungal infections have drawn attention recently to the problem of antifungal resistance and its underlying mechanisms. The number of fungal isolates that are resistant to the orally active azole antifungals, especially fluconazole, is growing. Amphotericin-B-resistant isolates have been recovered during treatment of patients with candidiasis, and resistance to flucytosine is so common that this antifungal is no longer recommended as a single-drug therapy.

Amphotericin B↗
PubMed1994

Pathogenesis of Candida infections.

Candida infections of the skin and superficial mucosal sites are the result of an interplay between fungal virulence and host defenses. Epidermal proliferation and T-lymphocyte immune responses are expressed by the host to combat fungal invasion, but inflammatory responses and nonspecific inhibitors also probably play a role. Candida albicans can express at least three types of surface adhesion molecules to colonize epithelial surfaces, plus an aspartyl proteinase enzyme able to facilitate initial penetration of keratinized cells. Deeper penetration of keratinized epithelia is assisted by hypha formation, and C. albicans hyphae may use contact sensing (thigmotropism) as a guiding mechanism. Pathogenesis requires differential expression of virulence factors at each new stage of the process: a propensity for rapid alteration of the expressed phenotype in C. albicans may therefore be a significant factor in establishing the comparatively high pathogenic potential of this species.

Animals↗
PubMed1994

CHROMagar Candida, a new differential isolation medium for presumptive identification of clinically important Candida species.

CHROMagar Candida is a novel, differential culture medium that is claimed to facilitate the isolation and presumptive identification of some clinically important yeast species. We evaluated the use of this medium with 726 yeast isolates, including 82 isolated directly on the medium from clinical material. After 2 days of incubation at 37 degrees C, 285 C. albicans isolates gave distinctive green colonies that were not seen with any of 441 other yeast isolates representing 21 different species. A total of 54 C. tropicalis isolates also developed distinctive dark blue-gray colonies with a halo of dark brownish purple in the surrounding agar. C. krusei isolates (n = 43) also formed highly characteristic rough, spreading colonies with pale pink centers and a white edge that was otherwise encountered only rarely with isolates of C. norvegensis. Trichosporon spp. (n = 34) formed small, pale colonies that became larger and characteristically rough with prolonged incubation. Most of the other 310 yeasts studied formed colonies with a color that ranged from white to pink to purple with a brownish tint. The only exceptions were found among isolates identified as Geotrichum sp. or Pichia sp., some of which formed colonies with a gray to blue color and which in two instances formed a green pigment or a dark halo in the agar. The specificity and sensitivity of the new medium for the presumptive identification of C. albicans, C. krusei, and C. tropicalis exceeded 99% for all three species. A blinded reading test involving four personnel and 57 yeast isolates representing nine clinically important species confirmed that colonial appearance after 48 h of incubation on CHROMagar Candida afforded the correct presumptive recognition of C. albicans, C. tropicalis, C, krusei, and Trichosporon spp. None of nine bacterial isolates grew on CHROMagar Candida within 72 h, and bacteria (Escherichia coli) grew from only 4 of 104 vaginal, 100 oral, and 99 anorectal swabs. The new medium supported the growth of 19 of 23 dermatophyte fungi tested and 41 of 43 other molds representing a broad range of fungal pathogens and contaminants. In parallel cultures of 348 clinical specimens set up on Sabourand agar and CHROMagar Candida, both media grew yeasts in the same 78 instances. CHROMagar Candida is recommended as a useful isolation medium capable of the presumptive identification of the yeast species most commonly isolated from clinical material and facilitating recognition of mixed yeast cultures.

Agar↗