Development of Reference Procedures for Broth Microdilution Antifungal Susceptibility Testing of Yeasts with Standardized Endpoint Determination

Makimura, Koichi; Sudo, Takako; Kudo, Michinari; Uchida, Katsuhisa; Yamaguchi, Hideyo

doi:10.1111/j.1348-0421.1998.tb01970.x

Cited by 12 publications

(18 citation statements)

References 15 publications

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“…Broth micro-dilution assay was performed according to the standard guidelines for the broth micro-dilution susceptibility test for yeast (18) or for filamentous fungus (22), with necessary modifications. The use of 96 flatshaped plastic microplates was avoided because of possible adsorption of water-insoluble components of essential oils on the plastic surface.…”

Section: Broth Micro-dilution Assay Under Open Conditionsmentioning

confidence: 99%

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Effect of Sealing and Tween 80 on the Antifungal Susceptibility Testing of Essential Oils

Inouye

Tsuruoka

Uchida

et al. 2001

Microbiology and Immunology

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Concentrations of essential oils showing high volatility decreased substantially in broth and agar media when incubated under open conditions. The decrease in the half life was from 0.7 to 38 hr in broth medium at 27 C. When evaporation was prevented by sealing, MIC values against Aspergillus jumigatus, Candida albicans and Trichophyton mentagrophytes by broth or agar dilution assay were lowered two to eight-fold, as compared with those obtained under open conditions. Addition of Tween 80 caused a rise of the MICs againstA.jumigatus by two to four-fold in broth dilution assay, but little affected the MICs in agar dilution assay.Key words: Antifungal test, Essential oils, Sealing, Tween 80Antifungal activity of essential oils has been determined by agar diffusion assay (1,2,7,20), broth or agar dilution assay (I, 17, 21, 24, 30) and assays to measure inhibition of mycelial growth (4, 9, 16, 23). These assays were originally developed to determine the activity of non-volatile and water soluble compounds, and their application to volatile and hydrophobic essential oils could not be justified unless assay conditions were adequately modified. A large number of papers have reported the in vitro antifungal activity of essential oils in solution, but, little systematic investigation has been done on the effect of sealing in the assay of essential oils in the aqueous phase. Sealing has usually been done to determine the antifungal activity of essential oils in the vapor state (8,19).Surface active agents such as Tween 80 were frequently used to obtain homogeneous suspension of essential oils in aqueous media (3, 4), but contradictory results have been reported on the effect of emulsifiers: one weakening the bioactivity (13,25), and the other increasing (28) or having little effect on the bioactivity (5) but giving good reproducibility (4, 11). The effect of Tween 80 to date examined mainly using bacterial strains, but no filamentous fungus has been tested.In the course of assaying essential oils by vapor contact using an agar dilution technique, we have found that some of these oils absorbed onto agar under sealing

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Section: Broth Micro-dilution Assay Under Open Conditionsmentioning

confidence: 99%

“…Then, conidia suspensions were prepared as described (10). A suspension of C. albicans was prepared utilizing the reference procedure reported (18).…”

mentioning

confidence: 99%

Effect of Sealing and Tween 80 on the Antifungal Susceptibility Testing of Essential Oils

Inouye

Tsuruoka

Uchida

et al. 2001

Microbiology and Immunology

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“…This kit was reported as equivalent to the JSMM standard method (2) and MIC values have been used after 24-hr incubation for almost all of the ascomycotic yeasts, including Candida species except C. glabrata and C. krusei (1,12). NCCLS recommended that 24-hr incubation is also meaningful because 24-hr MIC reading is often possible 104 K. MAKIMURA ET AL and 24-hr readings may be more clinically relevant for some isolates.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, there has been controversy regarding optimization of the incubation time for antifungal susceptibility testing (8). The JSMM microdilution method and its commercial version, frozen Eiken plates, were developed for reliable comparable antifungal susceptibility testing to the NCCLS M27-P macrodilution method (4) for five antifungal agents in 1994 (1,12). These aims were achieved using our endpoint reading system in which corrections were made for the differences in growth rates of tested cultures.…”

Section: Discussionmentioning

confidence: 99%

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Multicenter Evaluation of Commercial Frozen Plates for Microdilution Broth Antifungal Susceptibility Testing of Yeasts and Comparison of MIC Limits Recommended in NCCLS M27–A2

Makimura

Oguri

Mikami

et al. 2005

Microbiology and Immunology

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A commercial kit, Frozen Plate for Antifungal Susceptibility Testing of Yeasts, Eiken (Eiken Chemical Co., Ltd., Tokyo), was tested in a multi‐institute study to evaluate the agreement between inter‐institute MICs and National Committee for Clinical Laboratory Standards (NCCLS) M27–A2 recommendation limits of MIC value. The kit was reported as a method equivalent to the standardized guidelines for antifungal susceptibility testing by the Committee for Clinical Laboratory Standards—1994, the Japanese Society for Medical Mycology, and which is widely used in Japan for amphotericin B, flucytosine, fluconazole, miconazole, and itraconazole. The degrees of inter‐institute and NCCLS agreements were good to excellent especially with 48‐hr incubation for all antifungal agents. However, the percent agreements to NCCLS recommendations against itraconazole were poor. Overall, MIC values obtained using the frozen plate antifungal susceptibility testing kit, with 48‐hr incubation, were thought to be reliable and convenient alternatives to the data obtained by the NCCLS M27–A2 reference macrodilution and microdilution method. This kit will allow matching of results between international laboratories. However, the MIC value for itraconazole requires careful interpretation.

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Inhibitory effect of essential oils on apical growth of Aspergillus fumigatus by vapour contact

Inouye

Tsuruoka

Watanabe

et al. 2000

Mycoses

129

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The inhibitory effect of seven essential oils on the apical growth of hyphae of Aspergillus fumigatus was studied using a bio cell tracer by vapour contact in a sealed vessel. Based on the inhibitory pattern, these essential oils were classified into three groups. The first group, composed of citron, lavender and tea tree oils, stopped the apical growth in a loading dose of 63 micrograms ml-1 air, but allowed the regrowth of the hyphae after removal of the vapour, indicating fungistatic action. The second group, consisting of perilla and lemon-grass oils, stopped the apical growth in a loading dose of 6.3 micrograms ml-1 air, and did not allow the regrowth after gaseous contact at 63 micrograms ml-1 air, indicative of fungicidal action. The third group, consisting of cinnamon bark and thyme oils, retarded the growth in a dose of 6.3 micrograms ml-1 air, stopped it in a dose of 63 micrograms ml-1 air, and incompletely suppressed regrowth of the hyphae. Gas chromatographic analysis revealed that vapours of essential oils were absorbed on fungal mycelia and agar medium most abundantly by the first group, followed by the second and third groups, reflecting the volatility of the respective groups. Suppression of the apical growth by vapour contact was ascribed to the direct deposition of essential oils on fungal mycelia, together with an indirect effect via the agar medium absorbed.

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Development of Reference Procedures for Broth Microdilution Antifungal Susceptibility Testing of Yeasts with Standardized Endpoint Determination

Cited by 12 publications

References 15 publications

Effect of Sealing and Tween 80 on the Antifungal Susceptibility Testing of Essential Oils

Effect of Sealing and Tween 80 on the Antifungal Susceptibility Testing of Essential Oils

Multicenter Evaluation of Commercial Frozen Plates for Microdilution Broth Antifungal Susceptibility Testing of Yeasts and Comparison of MIC Limits Recommended in NCCLS M27–A2

Inhibitory effect of essential oils on apical growth of Aspergillus fumigatus by vapour contact

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