In Vitro Activities of Amphotericin B, Caspofungin, Itraconazole, Posaconazole, and Voriconazole against 45 Clinical Isolates of Zygomycetes: Comparison of CLSI M38-A, Sensititre YeastOne, and the Etest

Abstract

We evaluated the activities of amphotericin B, itraconazole, voriconazole, caspofungin, and posaconazole against zygomycetes by CLSI M38-A, Etest and Sensititre. The most active drug was posaconazole, followed by amphotericin B and itraconazole. The correlation of the Etest and Sensititre with CLSI M38-A was moderate for posaconazole but poor for the others.The incidence of zygomycosis is increasing in some institutions, purportedly due to voriconazole prophylaxis (16,19,20,22,23,25,28,31,32). The introduction of new antifungal agents and the availability of alternative antifungal susceptibility procedures necessitate studies comparing the in vitro activity of these new antifungal agents against zygomycetes.In this study, the in vitro activities of amphotericin B (AMB), itraconazole (ITC), voriconazole (VC), caspofungin (CAS), and posaconazole (POS) were assessed against 45 clinical strains of zygomycetes (Table 1). In addition, we compared the results obtained by the CLSI M38-A method with the Etest and Sensititre YeastOne.CLSI M38-A method. The antifungal drugs used were AMB (Sigma Chemical Co., St. Louis, MO), ITC (Janssen Pharmaceutical Research and Development, Madrid, Spain), VC (Pfizer Pharmaceutical Group, New York, NY), POS (ScheringPlough, Kenilworth, NJ), and CAS (Merck Research Laboratories, Rahway, NJ). The broth microdilution method was performed according to CLSI guidelines (21). The final concentration of the VC, ITC, POS, and AMB in the wells ranged from 0.03 to 16 g/ml. The final concentration of CAS in the wells ranged from 0.250 to 256 g/ml. The MIC endpoint was defined as the lowest concentration producing complete inhibition of growth (MIC-0) for all the antifungal drugs studied. The minimum effective concentration (MEC) endpoint for CAS was defined as the lowest concentration at which an abnormal growth was observed.Quality control was ensured by testing Aspergillus flavus ATCC 204304 and Aspergillus fumigatus ATCC 204305. All results were within the recommended limits of CLSI M38-A.Etest and Sensititre YeastOne procedures. Etest strips (AB Biodisk, Solna, Sweden) of ITC, VC, CAS, and AMB were supplied by Tec Laim (Madrid, Spain), and those of POS were supplied by Schering-Plough (Kenilworth, NJ). Inoculum suspensions were prepared in the same way as for the CLSI method. The MIC was defined as the lowest drug concentration at which the border of the elliptical inhibition zone intercepted the scale on the antifungal strip.The activities of AMB, VC, ITC, and CAS were studied by means of Sensititre YeastOne (Trek Diagnostic Systems, Ltd., East Grinstead, United Kingdom). The trays containing serial twofold dilutions of the drug (0.008 to 16 g/ml) were used. Inoculum suspensions were prepared in the same way as for the CLSI method, and the adjusted suspensions were diluted at 1:100 in RPMI.The CLSI microtiter panels, Sensititre panels, and Etest plates were incubated at 35°C and read after 16,24, 36, 48, and 72 h of incubation.We compared CLSI M38-A results (incubation at 24 h) with the altern...

Mucor circinelloides as a Cause of Invasive Maxillofacial Zygomycosis: an Emerging Dimorphic Pathogen with Reduced Susceptibility to Posaconazole

“…Posaconazole has a broad-spectrum of in vitro activity against yeasts, dimorphic fungi, and molds, including zygomycetes (23,36), and it has been successfully used in primary and salvage therapy for invasive zygomycosis (11,23,25). In fact, we seriously considered using posaconazole as a primary therapy in the present case.…”

“…A review of the antifungal susceptibility data indicates that Mucor species are relatively less susceptible to posaconazole than species of some other genera within the zygomycetes (Table 2). Recently Torres-Narbona et al (36) compared in vitro activities of posaconazole against 45 clinical isolates of zygomycetes that belonged to six different genera. Mucor species showed much higher MICs at which 90% of organisms were inhibited (2 g/ml) than species belonging to other genera (0.5 to 1.0 g/ml).…”

High-Throughput Identification and Quantification of Candida Species Using High Resolution Derivative Melt Analysis of Panfungal Amplicons

“…Offsetting this limitation, there is little indication that resolution beyond genus level is clinically important for Mucor, Rhizopus, or the other zygomyctes. 72,73 This is controversial among for Trichophyton spp., 74,75 and resolution of Penicillium marnefeii from other species of Penicillium may be important, but more susceptibility studies are needed to establish these needs. In the few samples in which species resolution is important but for which the melt analysis is ambiguous, it is always be an option to incorporate a second amplicon, or sequencing.…”

Diagnosis and treatment of mucormycosis in patients with hematological malignancies: guidelines from the 3rd European Conference on Infections in Leukemia (ECIL 3)

“…Compared with itraconazole and isavuconazole on a mg:mg basis, posaconazole has enhanced in vitro activity with reported 90% minimum inhibitory concentrations (MIC90) ranging from 1 to ≥ 4 mg/mL. 20,21,57,58,65,66 In the largest and most diverse collection of clinical isolates published so far, that included 217 clinical isolates of 11 species, 64-100% of the isolates were reported to be susceptible using an arbitrary breakpoint of 0.5 mg/mL or below. Comparatively higher MIC values were found for Mucor circinelloides 20 (Table 5).…”

“…20,21,[57][58][59] In the most comprehensive study presented so far, AmB was the most active antifungal agent with the majority of strains displaying MICs near the suggested breakpoint of ≤1 mg/mL (Table 5). Only some strains of Cunninghamella sp.…”