Istituto di Malattie Infettive e Medicina Pubblica, Università degli Studi di Ancona, Ospedale Umberto I, largo Cappelli 1, 60121 Ancona, Italy
Sir,
Fungal infections caused by common new and emerging yeast and mould pathogens are increasing in frequency, largely as a result of greater numbers of immunocompromised patients.1 Azole drugs are commonly used as treatment for patients with superficial and mild to moderate systemic mycoses, but 5-flucytosine (5FC) is administered, almost always in combination with amphotericin B, to most of those with severe systemic yeast and mould infections.2,3 The present study was undertaken to determine the susceptibilities to 5FC of 179 Candida spp. strains.
The isolates studied included 97 strains of Candida albicans, 30 of Candida tropicalis, 22 each of Candida parapsilosis and Candida glabrata and eight of Candida krusei. The strains were non-replicate and none of the patients from whom they were isolated had recently received antifungal therapy. Eighty-one strains (52 C. albicans, 22 C. glabrata and eight C. krusei) were isolated from human immunodeficiency virus (HIV)-infected patients, and the remaining 98 strains were recovered from HIV-negative patients. Susceptibility to 5FC was determined by a microbroth dilution method recommended by the National Committee for Clinical Laboratory Standards (NCCLS).4 5FC was tested at concentrations ranging from 0.125 to 64 mg/L and C. albicans ATCC 76615 and C. krusei ATCC 6258 were used as controls. Each strain was assigned to a susceptibility category according to the following MIC breakpoints recommended by the NCCLS:4 susceptible 4 mg/L; intermediate susceptibility 816 mg/L; and resistant
32 mg/L.
The results are summarized in the Table. Overall, 173/ 179 (97%) of the isolates were susceptible to 5FC, but 2/179 (1%) and 4/179 (2%) were intermediately susceptible and resistant, respectively. There was no statistically significant difference between isolates recovered from HIV-positive and HIV-negative patients in terms of susceptibility to 5FC (MannWhitney U test; P = 0.16).
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We identified two species, C. glabrata and C. krusei, whose isolates exhibited reduced susceptibility to 5FC. This observation suggests that the use of 5FC as treatment for patients with fungal infections caused by strains belonging to these species should be avoided unless they are known to be susceptible. To our knowledge this is the first report describing the patterns of susceptibility to 5FC among common clinical yeast isolates based on NCCLS interpretative breakpoints.
Notes
J Antimicrob Chemother 2000; 45: 408409
* Corresponding author. Tel: +39-71-596-3467; Fax: +39-71-596-3468; E-mail: cmalinf{at}popcsi.unian.it
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