[Antifungal susceptibility of yeasts by Etest. Comparison of 3 media].
BACKGROUND
The increasing frequency of systemic fungal infections and the emergency of secondary resistance to antifungals in the lasts years, has stimulated the use of methods for antifungal susceptibility testing. Etest is an easily performed quantitative method that has a good agreement with the broth microdilution reference method (NCCLS), if appropriate media are used.


OBJECTIVE
To compare the susceptibility to Amphotericin B (AmB) and Fluconazole (Flu) of 22 opportunistic yeast isolates (C albicans (7), C tropicalis (9), C parapsilosis (3) and Cryptococcus neoformans (3) by Etest, using three different media and to choose the best medium for each tested drug. The studied media were RPMI 1640, Casitone (Cas) and Sabouraud.


RESULTS
The interpretation of minimal inhibitory concentration (MIC) endpoints on Sabouraud was difficult for AmB. The American Type Culture Collection (ATCC) strains MICs were out of the acceptable range in this medium. RPMI and Cas were suitable media to test AmB and Flu, but best endpoints were obtained for AmB in RPMI and Flu in Cas.


CONCLUSIONS
The use of appropriate media for each antifungal drug optimizes the MIC readings by Etest. AmB should be tested in RMPI and Flu in Cas. Sabouraud must not be used.
Tapia
Cecilia
C
Laboratorio de Microbiologia, Pontificia Universidad Católica de Chile. cvtapia@entelchile.net
León
Eugenia
E
Palavecino
Elizabeth
E
D000666:Amphotericin B / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects / Q000254:growth & development; D015169:Colony Count, Microbial; D003455:Cryptococcus neoformans / Q000187:drug effects / Q000254:growth & development; D003470:Culture Media; D025141:Drug Resistance, Fungal; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D003904:Mitosporic Fungi / Q000187:drug effects* / Q000254:growth & development
D000935:Antifungal Agents; D003470:Culture Media; D000666:Amphotericin B; D015725:Fluconazole