Effects of pH on the Activity of Ketoconazole Against
            <i>Candida albicans</i>

Minagawa, Harushige; Kitaura, Kozo; Nakamizo, Nobuhiro

doi:10.1128/aac.23.1.105

Cited by 50 publications

(30 citation statements)

References 10 publications

(7 reference statements)

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“…This effect was moderate, changing the IC112s no more than 32-fold, and did not significantly affect the rank order susceptibilities of the yeasts tested. This has been reported with other azole antifungal agents (5,15).…”

Section: Discussionmentioning

confidence: 64%

In vitro susceptibilities of yeasts to a new antifungal triazole, SCH 39304: effects of test conditions and relation to in vivo efficacy

McIntyre

Galgiani

1989

Antimicrob Agents Chemother

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We used six candidal strains (two Candida albicans and one each of four other species) to study the effects of test conditions on the activity of SCH 39304 compared with that of fluconazole in broth macro-and microdilution assays. Increasing the inoculum from 102 to 105 yeasts per ml raised the MICs for all isolates up to >512-fold. In contrast, results with a 50% turbidimetric endpoint (50% inhibitory concentration; IC,,2) varied no more than twofold. Similar effects were seen with fluconazole, and both drugs were found to have an associated delay in onset of action. Acidity was found to increase both MICs and IC1,2s. Other effects were observed among four synthetic media, but a consistent pattern was not identified. (1-6, 8, 10, 12, 15, 16, 20 [7,18,23]) and one each of C. glabrata (R87), C. tropicalis (F26), C. parapsilosis (3288), and C. lusitaniae * Corresponding author.(ATCC 64125). In addition, 39 isolates of C. albicans were used. These included 32 strains from a panel selected for their variable susceptibilities to an unrelated antifungal agent, flucytosine (18, 21), and 7 strains selected from among clinical isolates from our collection. Another strain was isolated from a patient whose ketoconazole treatment failed (strain K3, also identified by others as KB [9,10,18]). A final C. albicans isolate, strain F662, used previously with strain C17 to evaluate the effect of inoculum size on results obtained with fluconazole (18), was also used for inoculum studies. Locally isolated clinical isolates of C. glabrata (six strains), C. tropicalis (three strains), and C. parapsilosis (three strains) were tested with a single set of conditions. Isolates which had been stored in yeast nitrogen broth (YNB; Difco Laboratories, Detroit, Mich.) with 10% glycerol at -70°C were thawed and maintained on Sabouraud dextrose 3% agar plates (Sab-Dex broth, BBL Microbiology Systems, Cockeysville, Md.; Bacto-Agar, Difco). For studies, subcultures were inoculated into. 20 ml of YNB and incubated at 37°C overnight.Media and buffers. A 2 x concentration of unbuffered SAAMF was prepared as previously described (11), except that cystine was replaced with equimolar amounts of cysteine (14); filter sterilized (cellulose nitrate membrane; pore size, 0.20 pum; Nalge Co., Rochester, N.Y.); and stored at 4°C. This was the medium used for all of the experiments, except when specifically noted otherwise. YNB was prepared as recommended by the manufacturer to a lOx concentration, filter sterilized, and stored at 4°C. Minimal essential medium with Hanks balanced salt solution and RPMI 1640 medium (both from Sigma) were prepared on the day of use as recommended by the manufacturer. YNB and SAAMF were diluted to lx with deionized water, and all media were buffered, adjusted to the appropriate pH, and sterilized by filtration.

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Section: Discussionmentioning

confidence: 64%

In vitro susceptibilities of yeasts to a new antifungal triazole, SCH 39304: effects of test conditions and relation to in vivo efficacy

McIntyre

Galgiani

1989

Antimicrob Agents Chemother

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“…By contrast the use of chemically complex undefined media such as SAB medium is not recommended (19,28) since undefined components that they may contain might interact with antifungal drugs (13,14,19,26). Furthermore, acidic media such as YNB and SAB, if they were used unbuffered, may inactivate amphotericin B, which is not stable at low pH (16,21).…”

Section: Discussionmentioning

confidence: 99%

Analysis of Growth Characteristics of Filamentous Fungi in Different Nutrient Media

et al. 2001

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A microbroth kinetic model based on turbidity measurements was developed in order to analyze the growth characteristics of three species of filamentous fungi (Rhizopus microsporus, Aspergillus fumigatus, and Scedosporium prolificans) characterized by different growth rates in five nutrient media (antibiotic medium 3, yeast nitrogen base medium, Sabouraud broth, RPMI 1640 alone, and RPMI 1640 with 2% glucose). In general, five distinct phases in the growth of filamentous fungi could be distinguished, namely, the lag phase, the first transition period, the log phase, the second transition period, and the stationary phase. The growth curves were smooth and were characterized by the presence of long transition periods. Among the different growth phases distinguished, the smallest variability in growth rates among the strains of each species was found during the log phase in all nutrient media. The different growth phases of filamentous fungi were barely distinguishable in RPMI 1640, in which the poorest growth was observed for all fungi even when the medium was supplemented with 2% glucose. R. microsporus and A. fumigatus grew better in Sabouraud and yeast nitrogen base medium than in RPMI 1640, with growth rates three to four times higher. None of the media provided optimal growth of S. prolificans. The germination of Rhizopus spores and Aspergillus and Scedosporium conidia commenced after 2 and 5 h of incubation, respectively. The elongation rates ranged from 39.6 to 26.7, 25.4 to 20.2, and 16.9 to 9.9 m/h for Rhizopus, Aspergillus, and Scedoporium hyphae, respectively. The germination of conidia and spores and the elongation rates of hyphae were enhanced in antibiotic medium 3 and delayed in yeast nitrogen base medium. In conclusion, the growth curves provide a useful tool to gain insight into the growth characteristics of filamentous fungi in different nutrient media and may help to optimize the methodology for antifungal susceptibility testing.

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“…The method for cell-free sterol biosynthesis was slightly modified from that of Kato and Kawase (5) and Marriott (7). Incubations (total, 1 ml) contained 929 ,ul of cell extract (protein, 8 to 10 mg/ml), 10 ,ul of dimethyl sulfoxide containing naftifine where appropriate, and 61 p.l of a substrate-cofactor cocktail (5). The substrate was 0.5 mM mevalonate containing 1 pCi of [2-14C]mevalonic acid lactone (Radiochemical Centre, Amersham, England).…”

Section: Methodsmentioning

confidence: 99%

“…to controls. For measuring the effects on lipid composition, cultures were grown for 24 h in Sabouraud medium buffered at pH 6.5 with 0.02 M Britton Robinson buffer (10) and inoculated with 107 cells per ml.…”

Section: Methodsmentioning

confidence: 99%

Effect of the antimycotic drug naftifine on growth of and sterol biosynthesis in Candida albicans

Ryder¹,

Seidl²,

Troke³

1984

Antimicrob Agents Chemother

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Naftifine, a new antimycotic drug of the allylamine class, is a potent inhibitor of ergosterol biosynthesis in Candida albicans. Treated cells showed a dose-dependent drop in ergosterol content; the level was reduced by 60% at concentrations of >50 mg/liter, causing total inhibition of growth. This inhibition coincided with a heavy accumulation of the sterol precursor squalene. Radiolabeling experiments showed that the inhibition of sterol synthesis was complete within 10 min of exposure of cells to the compound. Control cells incorporated [14C]acetate into nonsaponifiable lipids composed primarily of ergosterol, whereas naftifinetreated cells accumulated only labeled squalene. When the drug was removed by washing cells thoroughly in 1% Tween 80, the accumulated squalene was further metabolized to ergosterol. A similar pattern of inhibition was observed in sterol biosynthesis from [14C]mevalonate in a cell-free system. At 50 mg/liter, naftifine gave >99% inhibition of sterol biosynthesis both in whole cells and in cell extracts of C. albicans. The primary action of naftifine appears to be the blocking of fungal squalene epoxidation.Naftifine is an allylamine antimycotic drug with activity against a wide range of pathogenic fungi, particularly dermatophytes both in vitro (4) and in vivo (12). In clinical trials, the compound proved very effective as a topical treatment for dermatomycoses (3). At higher concentrations, naftifine also has in vitro activity against Candida albicans (4) and may be clinically useful against this organism. As naftifine represents an entirely new chemical class of antifungal agents, it is important to establish the mode of action in a range of target organisms. Earlier work with the dermatophyte Trichophyton mentagrophytes and the yeast Candida parapsilosis (11) indicated that naftifine interferes with ergosterol biosynthesis by blocking squalene metabolism. In this report, we describe the activity of naftifine against C. albicans, using several experimental models designed to quantify the effects on ergosterol biosynthesis in comparison with the inhibition of cell growth.( Extraction of lipids. Cells were harvested by centrifugation and treated by saponification in 50% ethanol containing 15% KOH and 0.1% pyrogallol for 2 h under reflux. After the addition of 2 volumes of water, the nonsaponifiable lipid (NSL) was extracted three times with petroleum ether (40 to 60°C). The petrol extract was washed with water, dried over anhydrous sodium sulfate, filtered, and brought to dryness in a rotary evaporator. NSL was dissolved in cyclohexane and stored at -20°C in the dark. For quantitative analysis, a known amount of cholesterol was added as an internal standard before the extraction.Gas chromatography. Components of NSL were separated by using a Siemens gas chromatograph (Sichromat 1) with a glass column (110 by 0.6 cm) with 1% OV3 silicone on Chromosorb G (Supelco, Inc., Bellefonte, Pa.) in the stationary phase. The carrier gas was helium (23 ml/min), and the temperature range program was ...

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Effects of pH on the Activity of Ketoconazole Against Candida albicans

Cited by 50 publications

References 10 publications

In vitro susceptibilities of yeasts to a new antifungal triazole, SCH 39304: effects of test conditions and relation to in vivo efficacy

In vitro susceptibilities of yeasts to a new antifungal triazole, SCH 39304: effects of test conditions and relation to in vivo efficacy

Analysis of Growth Characteristics of Filamentous Fungi in Different Nutrient Media

Effect of the antimycotic drug naftifine on growth of and sterol biosynthesis in Candida albicans

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