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M A Pfaller

Publications and source records attributed to M A Pfaller.

At least 37 records · Page 2Linked to original sources
PubMed2005

In vitro susceptibilities of clinical isolates of Candida species, Cryptococcus neoformans, and Aspergillus species to itraconazole: global survey of 9,359 isolates tested by clinical and laboratory standards institute broth microdilution methods.

The in vitro activity of itraconazole was determined against 7,299 isolates of Candida spp., 1,615 isolates of Cryptococcus neoformans, and 445 isolates of Aspergillus spp. obtained from over 200 medical centers worldwide. Itraconazole was active against all Candida spp. (96% of MICs were < or =1 microg/ml) with the exception of C. glabrata (77% of MICs were < or =1 microg/ml). Itraconazole inhibited 94% of C. krusei and 84% of other fluconazole-resistant Candida species, exclusive of C. glabrata, at a MIC of < or =1 microg/ml. Itraconazole was not active against fluconazole-resistant isolates of C. glabrata. Only modest activity was seen against C. neoformans (80% of MICs were < or =1 microg/ml); however, itraconazole showed excellent activity against Aspergillus spp. (94% of MICs were < or =1 microg/ml). These results provide an update on the antifungal activity of itraconazole against major opportunistic fungal pathogens. In light of the new intravenous formulation of itraconazole these data suggest that this agent remains a viable systemically active antifungal agent.

Antifungal Agents↗
PubMed2005

International and multicenter comparison of EUCAST and CLSI M27-A2 broth microdilution methods for testing susceptibilities of Candida spp. to fluconazole, itraconazole, posaconazole, and voriconazole.

The aim of this study was to compare MICs of fluconazole, itraconazole, posaconazole, and voriconazole obtained by the European Committee on Antibiotic Susceptibility Testing (EUCAST) and CLSI (formerly NCCLS) methods in each of six centers for 15 Candida albicans (5 fluconazole-resistant and 4 susceptible-dose-dependent [S-DD] isolates), 10 C. dubliniensis, 7 C. glabrata (2 fluconazole-resistant isolates), 5 C. guilliermondii (2 fluconazole-resistant isolates), 10 C. krusei, 9 C. lusitaniae, 10 C. parapsilosis, and 5 C. tropicalis (1 fluconazole-resistant isolate) isolates. CLSI MICs were obtained visually at 24 and 48 h and spectrophotometric EUCAST MICs at 24 h. The agreement (within a 3-dilution range) between the methods was species, drug, and incubation time dependent and due to lower EUCAST than CLSI MICs: overall, 94 to 95% with fluconazole and voriconazole and 90 to 91% with posaconazole and itraconazole when EUCAST MICs were compared against 24-h CLSI results. The agreement was lower (85 to 94%) against 48-h CLSI endpoints. The overall interlaboratory reproducibility by each method was > or =92%. When the comparison was based on CLSI breakpoint categorization, the agreement was 68 to 76% for three of the four species that included fluconazole-resistant and S-DD isolates; 9% very major discrepancies (< or =8 microg/ml versus > or =64 microg/ml) were observed among fluconazole-resistant isolates and 50% with voriconazole (< or =1 microg/ml versus > or =4 microg/ml). Similar results were observed with itraconazole for seven of the eight species evaluated (28 to 77% categorical agreement). Posaconazole EUCAST MICs were also substantially lower than CLSI MIC modes (0.008 to 1 microg/ml versus 1 to > or =8 microg/ml) for some of these isolates. Therefore, the CLSI breakpoints should not be used to interpret EUCAST MIC data.

Antifungal Agents↗
PubMed2005

Comparison of visual 24-hour and spectrophotometric 48-hour MICs to CLSI reference microdilution MICs of fluconazole, itraconazole, posaconazole, and voriconazole for Candida spp.: a collaborative study.

A multicenter (six-center) study evaluated the performance (interlaboratory reproducibility, compatibility with reference methods, and categorical agreement) of 24-h visual and 48-h spectrophotometric MICs. MICs of fluconazole, itraconazole, voriconazole, and posaconazole were compared to reference 48-h microdilution broth visual MICs (CLSI [formerly NCCLS] M27-A2 document) for 71 isolates of Candida spp. that included 10 fluconazole-resistant strains. Twenty readings (5%) were reported as showing no growth at 24 h, mostly for Candida dubliniensis and from a single center. The overall interlaboratory agreement of 24-h visual readings and 48-h spectrophotometric MICs, as well their compatibility with reference values, were excellent with the four triazoles for most of the species (93 to 99%, within 3 dilutions). The categorical agreement between the investigational reading conditions and reference values was good with fluconazole and voriconazole (93 to 97%) but lower with itraconazole (86 to 88%), due primarily to minor errors. There were only 0 to 3% very major errors with these three triazoles; the number of substantial errors (more than three dilutions) was also low (<2%) with posaconazole. These data suggest that the performance of both investigational MIC readings gives results similar to those of reference MICs. Since spectrophotometric MICs are more objective and the 24-h time period would shorten the MIC determination of azoles, the description of either of these two reading conditions in the M27-A2 document should be considered by the CLSI subcommittee in addition to or instead of the longer, less practical, and more subjective 48-h visual MIC reading.

Antifungal Agents↗
PubMed2005

Antifungal susceptibility testing methods.

The number of systemically active antifungal agents has increased dramatically in recent years in response to the challenge of invasive mycoses. Additional work is needed to better understand the mechanisms of action of these agents as well as the mechanisms of resistance expressed by the fungal pathogens. Antifungal susceptibility testing has been standardized and refined and now may be considered to play an important role in the management of invasive mycoses. More work is needed to optimize the methods for testing new antifungal agents and for testing pathogens other than Candida. The ongoing efforts and international collaborations designed to address these issues will provide important information that will improve the management of serious fungal infections.

Antifungal Agents↗
PubMed2004

In vitro activities of voriconazole, posaconazole, and fluconazole against 4,169 clinical isolates of Candida spp. and Cryptococcus neoformans collected during 2001 and 2002 in the ARTEMIS global antifungal surveillance program.

We examined the in vitro activities of voriconazole, posaconazole, and fluconazole against 3,932 isolates of Candida spp. and 237 isolates of Cryptococcus neoformans obtained from over 100 medical centers worldwide during 2001 and 2002. The MICs of the antifungal drugs were determined by broth microdilution tests performed according to the National Committee for Clinical Laboratory Standards (NCCLS) methods using RPMI 1640 as the test medium. Voriconazole and posaconazole were very active against Candida spp. (97-98% susceptible at MICs < or =1 microg/ml) and C. neoformans (98-100% susceptible at MICs < or =1 microg/mL). C. albicans (MIC90, 0.015-0.03 microg/ml) was the most susceptible species of Candida to both agents and C. glabrata (MIC90, 1-2 microg/mL) was the least susceptible. Both voriconazole and posaconazole were more active than fluconazole against all Candida spp. and C. neoformans. These results provide further evidence for the increased spectrum and potency of the new triazoles against a large and geographically diverse collection of opportunistic fungal pathogens.

Candida↗
PubMed2004

In vitro susceptibilities of rare Candida bloodstream isolates to ravuconazole and three comparative antifungal agents.

We determined the in vitro susceptibilities of 643 strains of Candida spp., representing 13 species rarely isolated from blood, to ravuconazole as well as three licensed systemic antifungal agents (amphotericin B, fluconazole, and flucytosine). The organisms included 234 isolates of C. krusei, 102 isolates of C. guilliermondii, 103 isolates of C. lusitaniae, 18 isolates of C. famata, 29 isolates of C. kefyr, 20 isolates of C. pelliculosa, 13 isolates of C. rugosa, 101 isolates of C. dubliniensis, 4 isolates of C. inconspicua, 11 isolates of C. lipolytica, 1 isolate of C. sake, and 2 isolates of C. lambica and 5 isolates of C. zeylanoides. MIC determinations were made by the National Committee for Clinical Laboratory Standards reference broth microdilution method and Etest (amphotericin B). Ravuconazole demonstrated excellent activity (98% susceptible at MIC < or = 1 microg/mL) against all species with the exception of C. inconspicua (75% [3 of 4]). By comparison, decreased susceptibility to fluconazole and/or amphotericin B was observed among isolates of C. krusei, C. guilliermondii, C. famata, C. rugosa, C. inconspicua, and C. lambica. These findings illustrate the fact that many of the less common species of Candida exhibit decreased susceptibility to one or more of the established systemically active antifungal agents. Ravuconazole is clearly an "extended-spectrum" triazole with potent in vitro activity against these rare and potentially "emerging" opportunistic pathogens.

Amphotericin B↗
PubMed2004

Clinical evaluation of a dried commercially prepared microdilution panel for antifungal susceptibility testing of five antifungal agents against Candida spp. and Cryptococcus neoformans.

A commercially prepared dried-broth microdilution panel (Sensititre, TREK Diagnostic Systems, Cleveland, OH) was compared with a reference frozen-broth microdilution panel for antifungal susceptibility testing of 728 clinical isolates of Candida spp. and 98 clinical isolates of Cryptococcus neoformans. The antifungal agents tested were amphotericin B, fluconazole, 5-fluorocytosine (5FC), itraconazole, and voriconazole. Microdilution testing was performed according to NCCLS recommendations. Minimum inhibitory concentration (MIC) endpoints were read visually after 48 hours of incubation (72 hours for C. neoformans) and were assessed independently for each microdilution panel. Discrepancies among MIC endpoints of no more than 2 log(2) dilutions were used to calculate the percentage of agreement. Overall levels of agreement between the study and reference panels were 98% for Candida spp. and 93% for C. neoformans. The agreement for each antifungal agent ranged from 96.6% for voriconazole to 99.4% for amphotericin B. The TREK dried microdilution panel appears to be a viable alternative to frozen-broth microdilution panels for testing of Candida spp. and C. neoformans.

Antifungal Agents↗
PubMed2004

Twelve years of fluconazole in clinical practice: global trends in species distribution and fluconazole susceptibility of bloodstream isolates of Candida.

We determined the species distribution and in-vitro susceptibility of 6082 bloodstream infection (BSI) isolates of Candida spp. collected from 250 medical centres in 32 nations over a 10-year period from 1992 through 2001. The species included 3401 C. albicans, 984 C. glabrata, 796 C. parapsilosis, 585 C. tropicalis, 153 C. krusei, 67 C. lusitaniae, 48 C. guilliermondii, 10 C. famata, 10 C. kefyr, six C. pelliculosa, five C. rugosa, four C. lipolytica, three C. dubliniensis, three C. inconspicua, two C. sake and one isolate each of C. lambica, C. norvegensis and C. zeylanoides. Minimum inhibitory concentration determinations were made using the National Committee for Clinical Laboratory Standards reference broth microdilution method. Variation in the rank order and frequency of the different species of Candida was observed over time and by geographic area. The proportion of BSI due to C. albicans and C. glabrata increased and C. parapsilosis decreased over time in Canada, the USA and Europe. C. glabrata was an infrequent cause of BSI in Latin America and the Asia-Pacific region. Very little variation in fluconazole susceptibility was observed among isolates of C. albicans, C. tropicalis and C. parapsilosis. These species accounted for 78% of all BSI and remained highly susceptible (91-100% susceptible) to fluconazole from 1992 to 2001 irrespective of geographic origin. The prevalence of fluconazole resistance among C. glabrata isolates was variable both over time and among the various countries and regions. Resistance to fluconazole among C. glabrata isolates was greatest in the USA and varied by US census region (range 0-23%). These observations are generally encouraging relative to the sustained usefulness of fluconazole as a systemically active antifungal agent for the treatment of candida BSI.

Antifungal Agents↗
PubMed2004

Determination of fungicidal activities against yeasts and molds: lessons learned from bactericidal testing and the need for standardization.

In certain unique clinical settings, the ability of the antimicrobial agent administered to kill the pathogen outright may be quite important. These situations invariably involve infection of a site not easily accessed by host defenses and/or of a structure with essential anatomic or physiologic function such as the heart (endocarditis), central nervous system (meningitis), or bone (osteomyelitis). Likewise, infections in immunosuppressed hosts, especially those who are neutropenic, are often thought to require microbicidal therapy. Proof of the cidal nature of an antimicrobial agent in vitro is tedious, complex, and fraught with error. Although several methods for assessing in vitro bactericidal activity have been standardized (NCCLS M26-A and M21-A), the clinical relevance of these determinations is questionable and the tests are performed infrequently in most laboratories. Most of the clinical data supporting the need for microbicidal therapy and testing have focused on bacterial infections. However, given the fact that most serious fungal infections occur in profoundly immunosuppressed individuals, it is generally assumed that a cidal regimen would be preferable in that setting as well. In view of this clinical concern and the perceived need to assess the fungicidal activity of a variety of agents, we considered that it would be useful to review what is known about the issues and problems in assessing bactericidal activity and the clinical utility of such measurements. Following this review, we discuss the issue of how one defines fungicidal activity in vitro and in vivo and how feasible it might be to determine the fungicidal activity of organism-drug combinations for purposes of both drug development and clinical care. Proposed methods for fungal time-kill determinations and minimal fungicidal concentration determinations are also discussed.

Animals↗
PubMed2004

Evaluation of the NCCLS M44-P disk diffusion method for determining susceptibilities of 276 clinical isolates of Cryptococcus neoformans to fluconazole.

We evaluated the NCCLS M44-P fluconazole disk diffusion method in comparison with the NCCLS M27-A2 broth microdilution method for determining the susceptibility of 276 isolates of Cryptococcus neoformans. Disk diffusion testing was performed using Mueller-Hinton agar supplemented with 2% glucose and 0.5 microg of methylene blue/ml. Among the 276 isolates, 259 (93.8%) were susceptible, 16 (5.8%) were susceptible--dose dependent, and 1 (0.4%) was resistant to fluconazole as determined by the NCCLS broth microdilution method. The overall categorical agreement between the two methods was 86%, with 0% very major errors, 2% major errors, and 12% minor errors. The disk diffusion method using Mueller-Hinton agar supplemented with glucose and methylene blue appears to be a useful approach for determining the fluconazole susceptibility of C. neoformans.

Antifungal Agents↗
PubMed2004

Clinical evaluation of the Sensititre YeastOne colorimetric antifungal plate for antifungal susceptibility testing of the new triazoles voriconazole, posaconazole, and ravuconazole.

A commercially prepared dried colorimetric microdilution panel (Sensititre YeastOne, TREK Diagnostic Systems, Cleveland, Ohio) was compared in three different laboratories with the National Committee for Clinical Laboratory Standards (NCCLS) reference microdilution method by testing two quality control strains and 300 clinical isolates of Candida spp. against fluconazole, voriconazole, posaconazole, and ravuconazole. Reference MIC endpoints were established after 48 h of incubation and YeastOne colorimetric endpoints were established after 24 h of incubation. YeastOne endpoints were determined to be the lowest concentration at which the color in the well changed from red (indicating growth) to purple (indicating growth inhibition) or blue (indicating no growth). Excellent agreement (within two dilutions) between the reference and colorimetric MICs was observed. Overall agreement was 95.4%. Agreement ranged from 92.3% with posaconazole to 98.0% with fluconazole. The YeastOne colorimetric method appears to be comparable to the NCCLS reference method for testing the susceptibility of Candida spp to the new triazoles voriconazole, posaconazole, and ravuconazole.

Antifungal Agents↗
PubMed2004

Evaluation of the etest method using Mueller-Hinton agar with glucose and methylene blue for determining amphotericin B MICs for 4,936 clinical isolates of Candida species.

The performance of the Etest using Mueller-Hinton agar supplemented with glucose (2%) and methylene blue (0.5 microg/ml) (MH-GMB) for amphotericin B susceptibility testing of 4,936 isolates of Candida spp. was assessed against that of Etest using RPMI agar with 2% glucose (RPG). MICs were determined by Etest in both media for all 4,936 isolates and were read after incubation for 48 h at 35 degrees C. The Candida isolates included C. albicans (n = 2,728), C. glabrata (n = 722), C. parapsilosis (n = 666), C. tropicalis (n = 528), C. krusei (n = 143), C. lusitaniae (n = 54), C. guilliermondii (n = 39), C. pelliculosa (n = 17), C. kefyr (n = 15), C. rugosa (n = 11), C. dubliniensis (n = 5), C. zeylanoides (n = 4), C. lipolytica (n = 3), and C. famata (n = 1). The Etest results with MH-GMB correlated well with those with RPG. Overall agreement was 92.9%, and agreements for individual species were as follows: C. lusitaniae, 98.1%; C. albicans, 95.1%; C. glabrata, 94.3%; C. krusei, 91.6%; C. parapsilosis, 86.6%; and C. tropicalis, 86.4%. The Etest method using MH-GMB appears to be a useful method for determining amphotericin B susceptibilities of Candida species.

Agar↗
PubMed2004

Stability of Mueller-Hinton agar supplemented with glucose and methylene blue for disk diffusion testing of fluconazole and voriconazole.

The shelf life of Mueller-Hinton agar supplemented with 2% glucose and methylene blue (0.5 micro g/ml) (MH-GMB) prepared in the laboratory to test disk diffusion of voriconazole and fluconazole was assessed using quality control (QC) strains of Candida albicans ATCC 90028, Candida krusei ATCC 6258, and Candida parapsilosis ATCC 22019. MH-GMB agar plates were prepared as described in National Committee for Clinical Laboratory Standards document M44-P, and isolates were tested using 25- micro g fluconazole disks and 1- micro g voriconazole disks over a 36-day period. Zone diameters for fluconazole and voriconazole varied by no more than 4 mm over the study period, and 95 to 100% of results were within the established QC limits for the strains tested. Prepared MH-GMB agar plates provide acceptable performance for disk diffusion testing for at least 30 days when stored at 5 degrees C.

Agar↗
PubMed2004

Quality control limits for voriconazole disk susceptibility tests on Mueller-Hinton agar with glucose and methylene blue.

An international collaborative study was performed in order to propose quality control limits for voriconazole disk diffusion tests on Mueller-Hinton agar with 2% glucose and 0.5 micro g of methylene blue per ml. The supplement may be added to the agar before autoclaving, or Mueller-Hinton agar plates may be flooded with a glucose-methylene blue solution. Replicate tests on both types of agar plates with 1- micro g voriconazole disks generated data to propose zone size limits for tests of Candida parapsilosis ATCC 22019 (28 to 37 mm), Candida albicans ATCC 90028 (31 to 42 mm), and Candida krusei ATCC 6258 (16 to 25 mm). Candida tropicalis ATCC 750 was not useful for this purpose.

Agar↗
PubMed2004

Intra- and interlaboratory study of a method for testing the antifungal susceptibilities of dermatophytes.

The National Committee for Clinical Laboratory Standards (NCCLS) M38-A standard for the susceptibility testing of conidium-forming filamentous fungi does not explicitly address the testing of dermatophytes. This multicenter study, involving six laboratories, investigated the MIC reproducibility of seven antifungal agents tested against 25 dermatophyte isolates (5 blinded pairs of five dermatophyte species per site for a total of 300 tests), using the method of dermatophyte testing developed at the Center for Medical Mycology, Cleveland, Ohio. The dermatophytes tested included Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton tonsurans, Epidermophyton floccosum, and Microsporum canis. Seven antifungals with activity against dermatophytes were tested, including ciclopirox, fluconazole, griseofulvin, itraconazole, posaconazole, terbinafine, and voriconazole. Interlaboratory MICs for all isolates were in 92 to 100% agreement at a visual endpoint reading of 50% inhibition as compared to the growth control and 88 to 99% agreement at a visual endpoint reading of 80% inhibition as compared to the growth control. Intralaboratory MICs between blinded pairs were in 97% agreement at a visual endpoint reading of 50% inhibition as compared to the growth control and 96% agreement at a visual endpoint reading of 80% inhibition as compared to the growth control. Data from this study support consideration of this method as an amendment to the NCCLS M38-A standard for the testing of dermatophytes.

Antifungal Agents↗
PubMed2004

Further standardization of broth microdilution methodology for in vitro susceptibility testing of caspofungin against Candida species by use of an international collection of more than 3,000 clinical isolates.

The influence of test variables on in vitro susceptibility testing of caspofungin was examined with 694 isolates of Candida albicans including seven laboratory-derived glucan synthesis mutants. The conditions providing the greatest separation between the mutant strains and the clinical isolates were RPMI medium, MIC end point criterion of partial inhibition, and incubation for 24 h. These testing conditions were then applied to 3,322 isolates of Candida spp. (3,314 clinical isolates and eight glucan synthesis mutants). Among the 11 isolates for which caspofungin MICs were >/=2 microg/ml, eight were accounted for by the glucan synthesis mutants. The MICs for >99% of isolates were </=1 microg/ml, and thus these isolates were differentiated from strains with reduced in vitro and in vivo susceptibilities to caspofungin.

Antifungal Agents↗
PubMed2004

Cross-resistance between fluconazole and ravuconazole and the use of fluconazole as a surrogate marker to predict susceptibility and resistance to ravuconazole among 12,796 clinical isolates of Candida spp.

Cross-resistance within a class of antimicrobial agents is a problem that is often encountered with antibacterial agents, and it is also an issue with antifungal agents. A current example is ravuconazole, a new triazole antifungal with an expanded spectrum and potency against Candida spp., Aspergillus spp., and other opportunistic fungal pathogens. The present study addresses the issue of cross-resistance between fluconazole and ravuconazole and the use of fluconazole as a surrogate marker to predict the susceptibility of Candida spp. to ravuconazole. Reference broth microdilution MIC results for 12,796 strains of Candida spp. isolated from more than 200 medical centers worldwide were used. Ravuconazole MICs and tentative interpretive categories (susceptible, </=1 microg/ml; resistant, >/=2 microg/ml) were compared with those of fluconazole by using regression statistics and error rate bounding analyses. For all 12,796 isolates, the absolute categorical agreement rate was 92.5% (rate of false-susceptible results, or very major errors [VME], 0.1%). Ravuconazole was active (MIC, </=1 microg/ml) against 99.9% of the fluconazole-susceptible isolates, 96% of the fluconazole-susceptible dose-dependent isolates, and 49% of the fluconazole-resistant isolates, including 99% of the Candida krusei isolates. Since ravuconazole is 16- to 32-fold more potent than fluconazole, the performance of fluconazole as a surrogate marker for ravuconazole susceptibility was improved by designating those isolates with fluconazole MICs of </=32 microg/ml susceptible to ravuconazole, resulting in a categorical agreement rate of 98.3%, with a VME rate of 0.3% (99 and 0.4%, respectively, when C. krusei was omitted). Cross-resistance between fluconazole and ravuconazole applies most directly to fluconazole-resistant Candida glabrata and is variable among other species of Candida. Fluconazole may serve as a surrogate marker to predict the susceptibility of Candida spp. to ravuconazole.

Antifungal Agents↗