Comparison of the Sensititre YeastOne colorimetric antifungal panel and Etest with the NCCLS M38-A method to determine the activity of amphotericin B and itraconazole against clinical isolates of Aspergillus spp.
OBJECTIVE
The evaluation of the Sensititre YeastOne and Etest methods for determining susceptibility to amphotericin B and itraconazole by comparing the MICs obtained by these methods at different times of reading with those of the M38-A broth microdilution method.


METHODS
Sixty-three clinical isolates of Aspergillus spp. (23 Aspergillus flavus, 24 Aspergillus fumigatus, nine Aspergillus niger, three Aspergillus glaucus, two Aspergillus terreus and two Aspergillus flavipes) were assayed. Two itraconazole-resistant strains (NCPF7100 and 7099) were also included.


RESULTS
Itraconazole MICs for the two resistant strains were >4 mg/L by the three methods. The overall agreement (+/-2 log2) between M38-A (48 h) and colorimetric (48 h) method was 93.4% for amphotericin B and 90.2% for itraconazole. By the Etest, the best agreement with M38-A was obtained when readings were made at 24 h: 88.5% for amphotericin B and 67.2% for itraconazole. Etest MICs were higher for all species except A. niger.


CONCLUSIONS
The colorimetric method appears to be a suitable alternative procedure for antifungal susceptibility testing of Aspergillus spp. and is able to detect resistance to itraconazole. The range of MICs for amphotericin B by Etest is wider and for some strains is >16 mg/L, suggesting that this method could be useful for detecting resistant strains as occur in yeasts.
Martín-Mazuelos
Estrella
E
Servicio de Microbiología, Hospital Universitario de Valme, Sevilla, Spain.
Pemán
Javier
J
Valverde
Anastasio
A
Chaves
Mónica
M
Serrano
M Carmen
MC
Cantón
Emilia
E
D000666:Amphotericin B / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D001228:Aspergillosis / Q000382:microbiology*; D001230:Aspergillus / Q000187:drug effects*; D003124:Colorimetry; D025141:Drug Resistance, Fungal; D006801:Humans; D017964:Itraconazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests / Q000295:instrumentation*; D015203:Reproducibility of Results
D000935:Antifungal Agents; D017964:Itraconazole; D000666:Amphotericin B