Antifungal Activity of 5-Fluorocytosine as Measured by Disk Diffusion Susceptibility Testing

Utz, C.; Shadomy, Smith

doi:10.1093/infdis/135.6.970

Cited by 28 publications

(8 citation statements)

References 2 publications

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“…In the United States, using this same definition, we found a resistance rate of 11.5 to 15.5% in four geographic centers and 35% at the fifth. This is comparable to the 21% rate of resistance reported in Montreal, Canada, by Auger et al (1) Earlier disk diffusion studies (12,19) showed better correlation between zone size and 48-h MICs than that reported here. Hutlet (11), however, noted a poor correlation between zone size and 24-h MICs.…”

Section: Discussionsupporting

confidence: 89%

Susceptibility to 5-fluorocytosine and prevalence of serotype in 402 Candida albicans isolates from the United States

Stiller¹,

Bennett²,

Scholer³

et al. 1982

Antimicrob Agents Chemother

101

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Candida albicans isolates from 402 patients with no prior history of treatment with 5-fluorocytosine were collected at five medical centers from different areas of the United States. Isolates could be separated into four groups based on their minimum inhibitory concentrations (MICs) to 5-fluorocytosine. Group I isolates (60%) had MICs less than or equal to 12.5 micrograms/ml after 7 days, whereas groups II (22%), III (14%), and IV (4%) demonstrated MICs greater than 12.5 micrograms/ml on days 7, 2, and 1, respectively. Serotypes A and B accounted for 50.7 and 49.3%, respectively, of the 398 isolates typed. Serotype B was less prevalent in group I (26%), but predominated in the more resistant groups, groups II (85%), III (86%), and IV (53%). The common practice of identifying as "resistant" those isolates with MICs greater than 12.5 micrograms/ml after 48 h of incubation would yield a resistance rate in the United States of 11.5 to 15.5% in four centers and 35% in the fifth. Although serotype B and small agar disk diffusion zone sizes correlated with poor 5-fluorocytosine susceptibility, their ability to predict tube dilution MICs was limited. The true predictive value of such tests awaits correlation with in vivo studies.

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Section: Discussionsupporting

confidence: 89%

Susceptibility to 5-fluorocytosine and prevalence of serotype in 402 Candida albicans isolates from the United States

Stiller¹,

Bennett²,

Scholer³

et al. 1982

Antimicrob Agents Chemother

101

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“…Disk Agar Diffusion (DAD) method [17] was used in this study. The plates were prepared by pouring about 15 mL of molten Sabouraud dextrose agar into sterile petri dishes.…”

Section: Methodsmentioning

confidence: 99%

Antimicrobial Activities of Hexane Extract and Decussatin from Stembark Extract of Ficus congensis

Alaribe

Shode

Coker

et al. 2011

IJMS

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Ficus congensis (Moraceae) is used traditionally in the treatment of various diseases including infectious diseases, infertility, and gastrointestinal disorders. Investigation of hexane extract of the stem bark using chromatographic techniques led to isolation of a xanthone, 1-hydroxy-3,7,8-trimethoxyxanthone (Decussatin). The compound was elucidated based on spectroscopic methods such as nuclear magnetic resonance (NMR), UV, IR, and mass spectrometry (MS). Decussatin and the hexane extract were screened in vitro for antibacterial and antifungal activities using broth microdilution (MHB) and disc Agar diffusion (DAD) techniques against Escheichia coli, Bacilus substilis, Klebsiela pneumonia, Staphylococcus aureus, Aspergillus fumigatus, Trichophyton mentagrophytes, Trichophyton rubrum and Candida albicans. Hexane extracts showed potent antibacterial activity against E. coli and B. subtilis with minimum inhibitory concentrations (MIC) of 8 mg/mL and 5 mg/mL, respectively, while Decussatin OPEN ACCESSInt. J. Mol. Sci. 2011, 12 2751 of the highest concentration (8 mg/mL) used in this study showed no appreciable antimicrobial activity. Only hexane extract was active against C. albicans with a MIC of 1 mg/mL.

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“…Such primary resistance to 5-FC has been seen in varying degrees with a relatively wide range of clinical isolates of various fungus species. With Candida spp., a number of reports were published from 1971 to 1982 (8, 13, 16,34,36,41,42,50,59,64,68,69,93,107,115,132,138,151,152,154,156,164,165,173,175,176). In those reports, the highest levels in the incidence of resistant isolates of C. albicans recorded so far were 37.2% found among 175 strains in Canada (93), and 25.8% found in the study of 58 isolates in the United States (175); intermediate levels, e.g.…”

Section: Flucytosine Resistancementioning

confidence: 99%

Drug resistance in human pathogenic fungi

Iwata

1992

Eur J Epidemiol

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Since the therapy of the mycoses, particularly the systemic mycoses, is relatively long-term in nature, emergence of resistance to antifungal drugs during the treatment of period would be of considerable clinical importance. However, most reports of resistance to antifungal agents among human pathogenic fungi indicate that naturally-occurring resistance is very rare, and that the induction of resistant mutants or variants is much more difficult to achieve in vitro and in vivo than with bacteria. As a matter of fact, amphotericin B and some other classic antifungals have not as yet posed a broadly significant problem relative to drug resistance despite their widespread and frequent use. Fungal resistance has thus received little attention, in contrast to the critical importance of bacterial resistance frequently caused by a variety of antibacterial chemotherapeutic agents, until a single exception to this generalization arose with the advent of flucytosine. This new development has aroused great interest in the problem of fungal resistance among the scientists involved with medical mycology. It is generally believed that fungi, like bacteria, are intrinsically capable of developing resistance to antifungal agents. As illustrated by flucytosine, inherently resistant mutants to antifungals occur within sensitive strains of human pathogenic fungi with significant frequency. Given the relatively high degree of such primary resistance, these mutants should develop secondary resistance during therapy, thus resulting in considerable limitations in the clinical usefulness of the antifungals. Virtually, all unsuccessful cases of mycoses treated with some of the recently exploited antifungal drugs, albeit scarce to date, would obviously be attributable to the occurrence of secondary resistance. The exploitation of new antifungal drugs thus requires investigations of their resistance as one of the most important research projects to be undertaken before receiving approval for use on humans. This paper reviews from various aspects the literature on resistance to various classic and novel antifungal agents among human pathogenic fungi. The resistance of some nonpathogenic fungi to these agents will also be described from genetic and biochemical points of view.

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Antifungal Activity of 5-Fluorocytosine as Measured by Disk Diffusion Susceptibility Testing

Cited by 28 publications

References 2 publications

Susceptibility to 5-fluorocytosine and prevalence of serotype in 402 Candida albicans isolates from the United States

Susceptibility to 5-fluorocytosine and prevalence of serotype in 402 Candida albicans isolates from the United States

Antimicrobial Activities of Hexane Extract and Decussatin from Stembark Extract of Ficus congensis

Drug resistance in human pathogenic fungi

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