Current antifungal agents cover a majority of opportunistic fungal pathogens; however, breakthrough invasive fungal infections continue to occur and increasingly involve relatively uncommon yeasts ...and molds, which often exhibit decreased susceptibility. APX001A (manogepix) is a first-in-class small-molecule inhibitor of the conserved fungal Gwt1 protein. This enzyme is required for acylation of inositol during glycosylphosphatidylinositol anchor biosynthesis. APX001A is active against the major fungal pathogens, i.e.,
(except
),
, and hard-to-treat molds, including
and
In this study, we tested APX001A and comparators against 1,706 contemporary clinical fungal isolates collected in 2017 from 68 medical centers in North America (37.3%), Europe (43.4%), the Asia-Pacific region (12.7%), or Latin America (6.6%). Among the isolates tested, 78.5% were
spp., 3.9% were non-
yeasts, including 30 (1.8%)
var.
isolates, 14.7% were
spp., and 2.9% were other molds. All isolates were tested by CLSI reference broth microdilution. APX001A (MIC
, 0.008 μg/ml; MIC
, 0.06 μg/ml) was the most active agent tested against
sp. isolates; corresponding anidulafungin, micafungin, and fluconazole MIC
values were 16- to 64-fold higher. Similarly, APX001A (MIC
, 0.25 μg/ml; MIC
, 0.5 μg/ml) was ≥8-fold more active than anidulafungin, micafungin, and fluconazole against
var.
Against
spp., AXP001A (50% minimal effective concentration MEC
, 0.015 μg/ml; MEC
, 0.03 μg/ml) was comparable in activity to anidulafungin and micafungin.
isolates (>98%) exhibited a wild-type phenotype for the mold-active triazoles (itraconazole, posaconazole, and voriconazole). APX001A was highly active against uncommon species of
, non-
yeasts, and rare molds, including 11 isolates of
spp. (MEC values, 0.015 to 0.06 μg/ml). APX001A demonstrated potent
activity against recent fungal isolates, including echinocandin- and fluconazole-resistant strains. The extended spectrum of APX001A was also notable for its potency against many less common but antifungal-resistant strains. Further studies are in progress to evaluate the clinical utility of the methyl phosphate prodrug, APX001, in difficult-to-treat resistant fungal infections.
Abstract Antifungal resistance continues to grow and evolve and complicate patient management, despite the introduction of new antifungal agents. In vitro susceptibility testing is often used to ...select agents with likely activity for a given infection, but perhaps its most important use is in identifying agents that will not work, i.e., to detect resistance. Standardized methods for reliable in vitro antifungal susceptibility testing are now available from the Clinical and Laboratory Standards Institute (CLSI) in the United States and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) in Europe. Data gathered by these standardized tests are useful (in conjunction with other forms of data) for calculating clinical breakpoints and epidemiologic cutoff values (ECVs). Clinical breakpoints should be selected to optimize detection of non–wild-type (WT) strains of pathogens, and they should be species-specific and not divide WT distributions of important target species. ECVs are the most sensitive means of identifying strains with acquired resistance mechanisms. Various mechanisms can lead to acquired resistance of Candida species to azole drugs, the most common being induction of the efflux pumps encoded by the MDR or CDR genes, and acquisition of point mutations in the gene encoding for the target enzyme (ERG11) . Acquired resistance of Candida species to echinocandins is typically mediated via acquisition of point mutations in the FKS genes encoding the major subunit of its target enzyme. Antifungal resistance is associated with elevated minimum inhibitory concentrations, poorer clinical outcomes, and breakthrough infections during antifungal treatment and prophylaxis. Candidemia due to Candida glabrata is becoming increasingly common, and C glabrata isolates are increasingly resistant to both azole and echinocandin antifungal agents. This situation requires continuing attention. Rates of azole-resistant Aspergillus fumigatus are currently low, but there are reports of emerging resistance, including multi-azole resistant isolates in parts of Europe.
We tested a global collection of Candida sp. strains against anidulafungin, caspofungin, and micafungin, using CLSI M27-A3 broth microdilution (BMD) methods, in order to define wild-type (WT) ...populations and epidemiological cutoff values (ECVs). From 2003 to 2007, 8,271 isolates of Candida spp. (4,283 C. albicans, 1,236 C. glabrata, 1,238 C. parapsilosis, 996 C. tropicalis, 270 C. krusei, 99 C. lusitaniae, 88 C. guilliermondii, and 61 C. kefyr isolates) were obtained from over 100 centers worldwide. The modal MICs (in μg/ml) for anidulafungin, caspofungin, and micafungin, respectively, for each species were as follows: C. albicans, 0.03, 0.03, 0.015; C. glabrata, 0.06, 0.03, 0.015; C. tropicalis, 0.03, 0.03, 0.015; C. kefyr, 0.06, 0.015, 0.06; C. krusei, 0.03, 0.06, 0.06; C. lusitaniae, 0.05, 0.25, 0.12; C. parapsilosis, 2, 0.25, 1; and C. guilliermondii, 2, 0.5. 05. The ECVs, expressed in μg/ml (percentage of isolates that had MICs that were less than or equal to the ECV is shown in parentheses) for anidulafungin, caspofungin, and micafungin, respectively, were as follows: 0.12 (99.7%), 0.12 (99.8%), and 0.03 (97.7%) for C. albicans; 0.25 (99.4%), 0.12 (98.5%), and 0.03 (98.2%) for C. glabrata; 0.12 (98.9%), 0.12 (99.4%), and 0.12 (99.1%) for C. tropicalis; 0.25(100%), 0.03 (100%), and 0.12 (100%) for C. kefyr; 0.12 (99.3%), 0.25 (96.3%), and 0.12 (97.8%) for C. krusei; 2 (100%), 0.5 (98.0%), and 0.5 (99.0%) for C. lusitaniae; 4 (100%), 1 (98.6%), and 4 (100%) for C. parapsilosis; 16 (100%), 4 (95.5%), and 4 (98.9%) for C. guilliermondii. These WT MIC distributions and ECVs will be useful in surveillance for emerging reduced echinocandin susceptibility among Candida spp. and for determining the importance of various FKS1 or other mutations.
The CLSI Antifungal Subcommittee followed the M23-A2 "blueprint" to develop interpretive MIC breakpoints for anidulafungin, caspofungin, and micafungin against Candida species. MICs of <=2 μg/ml for ...all three echinocandins encompass 98.8 to 100% of all clinical isolates of Candida spp. without bisecting any species group and represent a concentration that is easily maintained throughout the dosing period. Data from phase III clinical trials demonstrate that the standard dosing regimens for each of these agents may be used to treat infections due to Candida spp. for which MICs are as high as 2 μg/ml. An MIC predictive of resistance to these agents cannot be defined based on the data from clinical trials due to the paucity of isolates for which MICs exceed 2 μg/ml. The clinical data set included only three isolates from patients treated with an echinocandin (caspofungin) for which the MICs were >2 μg/ml (two C. parapsilosis isolates at 4 μg/ml and one C. rugosa isolate at 8 μg/ml). Based on these data, the CLSI subcommittee has decided to recommend a "susceptible only" breakpoint MIC of <=2 μg/ml due to the lack of echinocandin resistance in the population of Candida isolates thus far. Isolates for which MICs exceed 2 μg/ml should be designated "nonsusceptible" (NS). For strains yielding results suggestive of an NS category, the organism identification and antimicrobial-susceptibility test results should be confirmed. Subsequently, the isolates should be submitted to a reference laboratory that will confirm the results by using a CLSI reference dilution method.
Fluconazole in vitro susceptibility test results determined by the CLSI M44-A disk diffusion method for 11,240 isolates of noncandidal yeasts were collected from 134 study sites in 40 countries from ...June 1997 through December 2007. Data were collected for 8,717 yeast isolates tested with voriconazole from 2001 through 2007. A total of 22 different species/organism groups were isolated, of which Cryptococcus neoformans was the most common (31.2% of all isolates). Overall, Cryptococcus (32.9%), Saccharomyces (11.7%), Trichosporon (10.6%), and Rhodotorula (4.1%) were the most commonly identified genera. The overall percentages of isolates in each category (susceptible, susceptible dose dependent, and resistant) were 78.0%, 9.5%, and 12.5% and 92.7%, 2.3%, and 5.0% for fluconazole and voriconazole, respectively. Less than 30% of fluconazole-resistant isolates of Cryptococcus spp., Cryptococcus albidus, Cryptococcus laurentii, Trichosporon beigelii/Trichosporon cutaneum, Rhodotorula spp., Rhodotorula rubra/Rhodotorula mucilaginosa, and Rhodotorula glutinis remained susceptible to voriconazole. Emerging resistance to fluconazole was documented among isolates of C. neoformans from the Asia-Pacific, Africa/Middle East, and Latin American regions but not among isolates from Europe or North America. This survey documents the continuing broad spectrum of activity of voriconazole against opportunistic yeast pathogens but identifies several of the less common species with decreased azole susceptibility. These organisms may pose a future threat to optimal antifungal therapy and emphasize the importance of prompt and accurate species identification.
Abstract The CLSI established clinical breakpoints (CBPs) for caspofungin (CSF), micafungin (MCF) and anidulafungin (ANF) versus Candida. The same CBP (susceptible (S): MIC ≤ 2 mcg/ml; non-S: MIC > 2 ...mcg/ml) was applied to all echinocandins and species. More data now allow reassessment of these CBPs. We examined cases of echinocandin failure where both MICs and fks mutations were assessed; wild type (WT) MICs and epidemiological cutoff values (ECVs) for a large Candida collection; molecular analysis of fks hotspots for Candida with known MICs; and pharmacokinetic and pharmacodynamic (PK/PD) data. We applied these findings to propose new species-specific CBPs for echinocandins and Candida. Of 18 candidiasis cases refractory to echinocandins and with fks mutations, 28% (CSF), 58% (ANF) and 66% (MCF) had MICs in the S category using CBP of ≤2 mcg/ml, while 0–8% would be S using CBP of ≤0.25 mcg/ml. WT MIC distributions revealed ECV ranges of 0.03–0.25 mcg/ml for all major species except C. parapsilosis (1–4 mcg/ml) and C. guilliermondii (4–16 mcg/ml). Among Candida tested for fks mutations, only 15.7–45.1% of 51 mutants were detected using the CBP for NS of >2 mcg/ml. In contrast, a cutoff of >0.25 mcg/ml for C. albicans , C. tropicalis , C. krusei , and C. dubliniensis detected 85.6% (MCF) to 95.2% (CSF) of 21 mutant strains. Likewise, a cutoff of >0.12 mcg/ml for ANF and CSF and of >0.06 mcg/ml for MCF detected 93% (ANF) to 97% (CSF, MCF) of 30 mutant strains of C. glabrata . These data, combined with PK/PD considerations, support CBPs of ≤0.25 mcg/ml (S), 0.5 mcg/ml (I), ≥1 (R) for CSF/MCF/ANF and C. albicans , C. tropicalis and C. krusei and ≤2 mcg/ml (S), 4 mcg/ml (I), and ≥8 mcg/ml (R) for these agents and C. parapsilosis . The CBPs for ANF and CSF and C. glabrata are ≤0.12 mcg/ml (S), 0.25 mcg/ml (I), and ≥0.5 mcg/ml (R), whereas those for MCF are ≤0.06 mcg/ml (S), 0.12 mcg/ml (I), and ≥0.25 mcg/ml (R). New, species-specific CBPs for Candida and the echinocandins are more sensitive to detect emerging resistance associated with fks mutations, and better able to predict risk for clinical failure.
We report on the in vitro activity of the Hos2 fungal histone deacetylase (HDAC) inhibitor MGCD290 (MethylGene, Inc.) in combination with azoles against azole-resistant yeasts and molds. ...Susceptibility testing was performed by the CLSI M27-A3 and M38-A2 broth microdilution methods. Testing of the combinations (MGCD290 in combination with fluconazole, posaconazole, or voriconazole) was performed by the checkerboard method. The fractional inhibitory concentrations were determined and were defined as <0.5 for synergy, greater-than-or-equal0.5 but <4 for indifference, and greater-than-or-equal4 for antagonism. Ninety-one isolates were tested, as follows: 30 Candida isolates, 10 Aspergillus isolates, 15 isolates of the Zygomycetes order, 10 Cryptococcus neoformans isolates, 8 Rhodotorula isolates, 8 Fusarium isolates, 5 Trichosporon isolates, and 5 Scedosporium isolates. MGCD290 showed modest activity when it was used alone (MICs, 1 to 8 μg/ml) and was mostly active against azole-resistant yeasts, but the MICs against molds were high (16 to >32 μg/ml). MGCD290 was synergistic with fluconazole against 55 (60%) of the 91 isolates, with posaconazole against 46 (51%) of the 91 isolates, and with voriconazole against 48 (53%) of the 91 isolates. Synergy between fluconazole and MGCD290 was observed against 26/30 (87%) Candida isolates. All 23 of the 91 Candida isolates that were not fluconazole susceptible demonstrated a reduced fluconazole MIC that crossed an interpretive breakpoint (e.g., resistant MIC, greater-than-or-equal64 μg/ml to susceptible MIC, less-than or equal to8 μg/ml) when fluconazole was combined with MGCD290 at 0.12 to 4 μg/ml. The activity of fluconazole plus MGCD290 was also synergistic against 6/10 Aspergillus isolates. Posaconazole plus MGCD290 demonstrated synergy against 14/15 Zygomycetes (9 Rhizopus isolates and 5 Mucor isolates). Voriconazole plus MGCD290 demonstrated synergy against six of eight Fusarium isolates. Thus, MGCD290 demonstrated in vitro synergy with azoles against the majority of clinical isolates tested, including many azole-resistant isolates and genera inherently resistant to azoles (e.g., Mucor and Fusarium). Further evaluation of fungal HDAC inhibitor-azole combinations is indicated.
The CLSI epidemiological cutoff values (ECVs) of antifungal agents are available for various Candida spp., Aspergillus spp., and the Mucorales. However, those categorical endpoints have not been ...established for Fusarium spp., mostly due to the difficulties associated with collecting sufficient CLSI MICs for clinical isolates identified according to the currently recommended molecular DNA-PCR-based identification methodologies. CLSI MIC distributions were established for 53 Fusarium dimerum species complex (SC), 10 F. fujikuroi, 82 F. proliferatum, 20 F. incarnatum-F. equiseti SC, 226 F. oxysporum SC, 608 F. solani SC, and 151 F. verticillioides isolates originating in 17 laboratories (in Argentina, Australia, Brazil, Canada, Europe, Mexico, and the United States). According to the CLSI guidelines for ECV setting, ECVs encompassing ≥97.5% of pooled statistically modeled MIC distributions were as follows: for amphotericin B, 4 μg/ml (F. verticillioides) and 8 μg/ml (F. oxysporum SC and F. solani SC); for posaconazole, 2 μg/ml (F. verticillioides), 8 μg/ml (F. oxysporum SC), and 32 μg/ml (F. solani SC); for voriconazole, 4 μg/ml (F. verticillioides), 16 μg/ml (F. oxysporum SC), and 32 μg/ml (F. solani SC); and for itraconazole, 32 μg/ml (F. oxysporum SC and F. solani SC). Insufficient data precluded ECV definition for the other species. Although these ECVs could aid in detecting non-wild-type isolates with reduced susceptibility to the agents evaluated, the relationship between molecular mechanisms of resistance (gene mutations) and MICs still needs to be investigated for Fusarium spp.
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