Background. Clinical isolates of Candida lusitaniae (CL), Aspergillus terreus (AT), and Aspergillus nidulans (AN) have been reported to be less susceptible to amphotericin B (AmB) than Candida albicans (CA) and Aspergillus fumigatus (AF), respectively. The aim of this study was to check the in vitro susceptibilities to AmB of clinical isolates of CL, AT, and AN from the University Hospital of Heidelberg, Germany, and compare them to control strains of CA and AF. Materials and methods. We tested a total of 63 isolates, including 23 CL, 8 CA, 13 AT, 9 AN, and 10 AF strains, using nine in vitro experimental settings each. Microdilution (M), Etest (E), and disc diffusion (D) methods were performed with three media each: RPMI 1640, antibiotic medium 3 (AM3), and high resolution medium (HR). The M assays were performed according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS). Results. The geometric means (GM) of the minimal inhibitory concentations (MICs) of CL ranged from 0.02 to 0.50 µg/ml, and the arithmetic means (AM) of the zones of inhibition of CL were 22.7, 23.4, and 22.7 mm. There was no significant difference between the susceptibilities of the CL and the CA isolates (P > 0.01) in seven of nine experimental settings. With M and E performed on AM3, CL was found even more susceptible than CA (GMs of MICs 0.04 vs 0.09 µg/ml, P = 0.01, and 0.02 vs 0.05 µg/ml, P = 0.0002, respectively). The GMs of the MICs of AT ranged from 1.10 to 7.28 µg/ml, and the AMs of the zones of inhibition of AT were 13.7, 13.5, and 9.8 mm. When compared with AF (GMs of MICs ranging from 0.07 to 0.66 µg/ml, AMs of zones of inhibition 19.2, 19.9, and 18.1 mm), the AT isolates were found significantly less susceptible in all nine experimental settings (P values ranging from 0.009 to 0.00001). The GMs of the MICs of AN ranged from 0.17 to 1.08 µg/ml, and the AMs of the zones of inhibition of AN were 17.1, 18.2, and 19.3 mm. There was no significant difference between the susceptibilities of the AN and the AF isolates (P > 0.01) in seven of nine experimental settings. With M performed with RPMI, AN was found slightly more susceptible than AF (GMs of MICs 0.29 vs 0.62 µg/ml, P = 0.01) and with M performed with AM3, AN was found slightly less susceptible than AF (GMs of MICs 0.17 vs 0.07, P = 0.007). Conclusions. As previously reported for other AT strains, 13 clinical AT isolates from Heidelberg, Germany, were significantly less susceptible to AmB than 10 AF control strains. However, 23 clinical isolates of CL and 9 of AN had similar susceptibilities to AmB as CA and AF control strains, respectively.
Full conference title:
The 15 th Congress of the International Society for Human and Animal Mycology
- ISHAM 15th (2003)