scholarly journals Interactions between Triazoles and Amphotericin B against Cryptococcus neoformans

2000 ◽  
Vol 44 (9) ◽  
pp. 2435-2441 ◽  
Author(s):  
Francesco Barchiesi ◽  
Anna M. Schimizzi ◽  
Francesca Caselli ◽  
Andrea Novelli ◽  
Stefania Fallani ◽  
...  
Keyword(s):  
Combination Therapy ◽  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Clinical Laboratory ◽  
Fungal Infections ◽  
National Committee ◽  
Positive Interaction ◽  
Pronounced Increase

ABSTRACT The interaction of amphotericin B (AmB) and azole antifungal agents in the treatment of fungal infections is still a controversial issue. A checkerboard titration broth microdilution-based method that adhered to the recommendations of the National Committee for Clinical Laboratory Standards was applied to study the in vitro interactions of AmB with fluconazole (FLC), itraconazole (ITC), and the new investigational triazole SCH 56592 (SCH) against 15 clinical isolates ofCryptococcus neoformans. Synergy, defined as a fractional inhibitory concentration (FIC) index of ≤0.50, was observed for 7% of the isolates in studies of the interactions of both FLC-AmB and ITC-AmB and for 33% of the isolates in studies of the SCH-AmB interactions; additivism (FICs, >0.50 to 1.0) was observed for 67, 73, and 53% of the isolates in studies of the FLC-AmB, ITC-AmB, and SCH-AmB interactions, respectively; indifference (FICs, >1.0 to ≤2.0) was observed for 26, 20, and 14% of the isolates in studies of the FLC-AmB, ITC-AmB, and SCH-AmB interactions, respectively. Antagonism (FIC >2.0) was not observed. When synergy was not achieved, there was still a decrease, although not as dramatic, in the MIC of one or both drugs when they were used in combination. To investigate the effects of FLC-AmB combination therapy in vivo, we established an experimental model of systemic cryptococcosis in BALB/c mice by intravenous injection of cells of C. neoformans 2337, a clinical isolate belonging to serotype D against which the combination of FLC and AmB yielded an additive interaction in vitro. Both survival and tissue burden studies showed that combination therapy was more effective than FLC alone and that combination therapy was at least as effective as AmB given as a single drug. On the other hand, when cells of C. neoformans 2337 were grown in FLC-containing medium, a pronounced increase in resistance to subsequent exposures to AmB was observed. In particular, killing experiments conducted with nonreplicating cells showed that preexposure to FLC abolished the fungicidal activity of the polyene. However, this apparent antagonism was not observed in vivo. Rather, when the two drugs were used sequentially for the treatment of systemic murine cryptococcosis, a reciprocal potentiation was often observed. Our study shows that (i) the combination of triazoles and AmB is significantly more active than either drug alone against C. neoformans in vitro and (ii) the concomitant or sequential use of FLC and AmB for the treatment of systemic murine cryptococcosis results in a positive interaction.

scholarly journals Melanization of Cryptococcus neoformans and Histoplasma capsulatum Reduces Their Susceptibilities to Amphotericin B and Caspofungin

2002 ◽  
Vol 46 (11) ◽  
pp. 3394-3400 ◽  
Author(s):  
David van Duin ◽  
Arturo Casadevall ◽  
Joshua D. Nosanchuk
Keyword(s):  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Fungal Pathogens ◽  
Histoplasma Capsulatum ◽  
Clinical Laboratory ◽  
National Committee ◽  
Broth Macrodilution ◽  
Mammalian Infection

ABSTRACT The fungal pathogens Cryptococcus neoformans and Histoplasma capsulatum produce melanin-like pigments in the presence of l-dopa in vitro and during mammalian infection. We investigated whether melanization affected the susceptibilities of the fungi to amphotericin B, caspofungin, fluconazole, itraconazole, or flucytosine (5FC). Using the standard macrodilution MIC protocol (the M27A protocol) of the National Committee for Clinical Laboratory Standards for yeast, we found no difference in the susceptibilities of melanized and nonmelanized C. neoformans and H. capsulatum isolates. Killing assays demonstrated that melanization reduced the susceptibilities of both fungi to amphotericin B and caspofungin. Laccase-deficient C. neoformans cells grown with l-dopa were significantly more susceptible than congenic melanin-producing yeast to killing by amphotericin B or caspofungin. Preincubation of amphotericin B or caspofungin with melanins decreased their antifungal activities. Elemental analysis of melanins incubated with amphotericin B or caspofungin revealed an alteration in the C:N ratios of the melanins, which indicated binding of these drugs by the melanins. In contrast, incubation of fluconazole, itraconazole, or 5FC with melanins did not significantly affect the antifungal efficacies of the drugs or the chemical composition of the melanins. The results suggest a potential explanation for the inefficacy of caspofungin against C. neoformans in vivo, despite activity in vitro. Furthermore, the results indicate that fungal melanins protect C. neoformans and H. capsulatum from the activities of amphotericin B and caspofungin and that this protection is not demonstrable by standard broth macrodilution assays.

scholarly journals Interactions of Posaconazole and Flucytosine against Cryptococcus neoformans

2001 ◽  
Vol 45 (5) ◽  
pp. 1355-1359 ◽  
Author(s):  
Francesco Barchiesi ◽  
Anna Maria Schimizzi ◽  
Laura K. Najvar ◽  
Rosie Bocanegra ◽  
Francesca Caselli ◽  
...  
Keyword(s):  
Combination Therapy ◽  
Cryptococcus Neoformans ◽  
Clinical Laboratory ◽  
Combined Therapy ◽  
Antifungal Susceptibility ◽  
National Committee ◽  
Treatment Groups ◽  
Beneficial Effects

ABSTRACT A checkerboard methodology, based on standardized methods proposed by the National Committee for Clinical Laboratory Standards for broth microdilution antifungal susceptibility testing, was applied to study the in vitro interactions of flucytosine (FC) and posaconazole (SCH 56592) (FC-SCH) against 15 isolates of Cryptococcus neoformans. Synergy, defined as a fractional inhibitory concentration (FIC) index of <0.50, was observed for 33% of the isolates tested. When synergy was not achieved, there was still a decrease in the MIC of one or both drugs when they were used in combination. Antagonism, defined as a FIC of >4.0, was not observed. The in vitro efficacy of combined therapy was confirmed by quantitative determination of the CFU of C. neoformans 486, an isolate against which the FC-SCH association yielded a synergistic interaction. To investigate the potential beneficial effects of this combination therapy in vivo, we established two experimental murine models of cryptococcosis by intracranial or intravenous injection of cells ofC. neoformans 486. At 1 day postinfection, the mice were randomized into different treatment groups. One group each received each drug alone, and one group received the drugs in combination. While combination therapy was not found to be significantly more effective than each single drug in terms of survival, tissue burden experiments confirmed the potentiation of antifungal activity with the combination. Our study demonstrates that SCH and FC combined are significantly more active than either drug alone against C. neoformans in vitro as well in vivo. These findings suggest that this therapeutic approach could be useful in the treatment of cryptococcal infections.

scholarly journals Trends in Antifungal Drug Susceptibility of Cryptococcus neoformans Isolates in the United States: 1992 to 1994 and 1996 to 1998

2001 ◽  
Vol 45 (11) ◽  
pp. 3065-3069 ◽  
Author(s):  
Mary E. Brandt ◽  
Michael A. Pfaller ◽  
Rana A. Hajjeh ◽  
Richard J. Hamill ◽  
Peter G. Pappas ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Antifungal Agents ◽  
Clinical Laboratory ◽  
The United States ◽  
Drug Susceptibility ◽  
Antifungal Drug ◽  
National Committee ◽  
Broth Microdilution Method

ABSTRACT The antifungal drug susceptibilities of two collections ofCryptococcus neoformans isolates obtained through active laboratory-based surveillance from 1992 to 1994 (368 isolates) and 1996 to 1998 (364 isolates) were determined. The MICs of fluconazole, itraconazole, and flucytosine were determined by the National Committee for Clinical Laboratory Standards broth microdilution method; amphotericin B MICs were determined by the E-test. Our results showed that the MIC ranges, the MICs at which 50% of isolates are inhibited (MIC50s), and the MIC90s of these four antifungal agents did not change from 1992 to 1998. In addition, very small numbers of isolates showed elevated MICs suggestive of in vitro resistance. The MICs of amphotericin B were elevated (≥2 μg/ml) for 2 isolates, and the MICs of flucytosine were elevated (≥32 μg/ml) for 14 isolates. Among the azoles, the fluconazole MIC was elevated (≥64 μg/ml) for 8 isolates and the itraconazole MIC (≥1 μg/ml) was elevated for 45 isolates. Analysis of 172 serial isolates from 71 patients showed little change in the fluconazole MIC over time. For isolates from 58 patients (82% of serial cases) there was either no change or a twofold change in the fluconazole MIC. In contrast, for isolates from seven patients (12% of serial cases) the increase in the MIC was at least fourfold. For isolates from another patient there was a 32-fold decrease in the fluconazole MIC over a 1-month period. We conclude that in vitro resistance to antifungal agents remains uncommon in C. neoformans and has not significantly changed with time during the past decade.

scholarly journals In vitro susceptibilities of clinical and environmental isolates of Cryptococcus neoformans to five antifungal drugs.

1996 ◽  
Vol 40 (3) ◽  
pp. 822-824 ◽  
Author(s):  
S P Franzot ◽  
J S Hamdan
Keyword(s):  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Clinical Laboratory ◽  
Antifungal Drugs ◽  
Clinical Isolates ◽  
National Committee ◽  
Environmental Isolates ◽  
Susceptibility Data

A total of 53 Cryptococcus neoformans strains, including clinical and environmental Brazilian isolates, were tested for their susceptibilities to amphotericin B, 5-flucytosine, ketoconazole, fluconazole, and itraconazole. The tests were performed according to the National Committee of Clinical Laboratory Standards recommendations (document M27-P). In general, there was a remarkable homogeneity of results for all strains, and comparable MICs were found for environmental and clinical isolates. This paper represents the first contribution in which susceptibility data for Brazilian C. neoformans isolates are provided.

In Vitro Activities of Voriconazole (UK-109,496) and Four Other Antifungal Agents against 394 Clinical Isolates ofCandida spp.

1998 ◽  
Vol 42 (1) ◽  
pp. 161-163 ◽  
Author(s):  
F. Marco ◽  
M. A. Pfaller ◽  
S. Messer ◽  
R. N. Jones
Keyword(s):  
Amphotericin B ◽  
Antifungal Agents ◽  
Clinical Laboratory ◽  
Candida Krusei ◽  
Antifungal Drugs ◽  
National Committee ◽  
In Vitro Activity ◽  
Medical Centers

ABSTRACT Voriconazole (formerly UK-109,496) is a new monotriazole antifungal agent which has potent activity against Candida,Cryptococcus, and Aspergillus species. We investigated the in vitro activity of voriconazole compared to those of fluconazole, itraconazole, amphotericin B, and flucytosine (5FC) against 394 bloodstream isolates of Candida (five species) obtained from more than 30 different medical centers. MICs of all antifungal drugs were determined by the method recommended by the National Committee for Clinical Laboratory Standards using RPMI 1640 test medium. Overall, voriconazole was quite active against all the yeast isolates (MIC at which 90% of the isolates are inhibited [MIC90], ≤0.5 μg/ml). Candida albicans was the most susceptible species (MIC90, 0.06 μg/ml) andCandida glabrata and Candida krusei were the least (MIC90, 1 μg/ml). Voriconazole was more active than amphotericin B and 5FC against all species except C. glabrata and was also more active than itraconazole and fluconazole. For isolates of Candida spp. with decreased susceptibility to fluconazole and itraconazole MICs of voriconazole were also higher. Based on these results, voriconazole has promising antifungal activity and further in vitro and in vivo investigations are warranted.

scholarly journals Comparative Evaluation of FUNGITEST and Broth Microdilution Methods for Antifungal Drug Susceptibility Testing of Candida Species and Cryptococcus neoformans

1998 ◽  
Vol 36 (4) ◽  
pp. 926-930 ◽  
Author(s):  
Kate G. Davey ◽  
Ann D. Holmes ◽  
Elizabeth M. Johnson ◽  
Adrien Szekely ◽  
David W. Warnock
Keyword(s):  
Cryptococcus Neoformans ◽  
Amphotericin B ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
National Committee ◽  
Broth Microdilution ◽  
Fluconazole Resistant

The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a microplate-based procedure for the breakpoint testing of six antifungal agents (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). We compared the FUNGITEST method with a broth microdilution test, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 180 isolates ofCandida spp. (50 C. albicans, 50C. glabrata, 10 C. kefyr, 20C. krusei, 10 C. lusitaniae, 20C. parapsilosis, and 20 C. tropicalisisolates) and 20 isolates of Cryptococcus neoformans. Overall, there was 100% agreement between the methods for amphotericin B, 95% agreement for flucytosine, 84% agreement for miconazole, 83% agreement for itraconazole, 77% agreement for ketoconazole, and 76% agreement for fluconazole. The overall agreement between the methods exceeded 80% for all species tested with the exception ofC. glabrata (71% agreement). The poorest agreement between the results for individual agents was seen with C. glabrata (38% for fluconazole, 44% for ketoconazole, and 56% for itraconazole) and C. tropicalis (50% for miconazole). The FUNGITEST method misclassified as susceptible 2 of 12 (16.6%) fluconazole-resistant isolates, 2 of 10 (20%) itraconazole-resistant isolates, and 4 of 8 (50%) ketoconazole-resistant isolates of several Candida spp. Further development of the FUNGITEST procedure will be required before it can be recommended as an alternative method for the susceptibility testing of Candida spp. or C. neoformans.

scholarly journals In vitro susceptibilities of clinical yeast isolates to a new echinocandin derivative, LY303366, and other antifungal agents.

1997 ◽  
Vol 41 (4) ◽  
pp. 763-766 ◽  
Author(s):  
M A Pfaller ◽  
S A Messer ◽  
S Coffman
Keyword(s):  
Amphotericin B ◽  
Fungicidal Activity ◽  
Antifungal Agents ◽  
Candida Parapsilosis ◽  
Clinical Laboratory ◽  
National Committee ◽  
In Vitro Activity ◽  
Medical Centers

LY303366 is a new semisynthetic echinocandin derivative with potent, broad-spectrum fungicidal activity. We investigated the in vitro activity of LY303366, amphotericin B, flucytosine (5FC), fluconazole, and itraconazole against 435 clinical yeast isolates (413 Candida and 22 Saccharomyces cerevisiae isolates) obtained from over 30 different medical centers. MICs for all five antifungal agents were determined by the National Committee for Clinical Laboratory Standards method with RPMI 1640 test medium. LY303366 was also tested in antibiotic medium 3 as specified by the manufacturer. Overall, LY303366 was quite active against all of the yeast isolates when tested in RPMI 1640 (MIC at which 90% of the isolates are inhibited [MIC90], 1.0 microg/ml) but appeared to be considerably more potent when tested in antibiotic medium 3 (MIC90, 0.03 microg/ml). When tested in antibiotic medium 3, LY303366 was 16- to >2,000-fold more active than itraconazole, fluconazole, amphotericin B, or 5FC against all species except Candida parapsilosis. When tested in RPMI 1640, LY303366 was comparable to amphotericin B and itraconazole and more active than fluconazole and 5FC. All of the isolates for which fluconazole and itraconazole had elevated MICs (> or = 128 and > or = 2.0 microg/ml, respectively) were inhibited by < or = 0.007 microg of LY303366/ml when tested in antibiotic medium 3 and < or = 0.5 microg/ml when tested in RPMI 1640. Based on these studies, LY303366 has promising antifungal activity and warrants further in vitro and in vivo investigation.

In vitro and in vivo activities of SCH 56592 against Blastomyces dermatitidis.

1996 ◽  
Vol 40 (5) ◽  
pp. 1314-1316 ◽  
Author(s):  
A M Sugar ◽  
X P Liu
Keyword(s):  
Amphotericin B ◽  
Clinical Laboratory ◽  
Blastomyces Dermatitidis ◽  
National Committee ◽  
High Dose ◽  
Triazole Derivative ◽  
In Vitro Susceptibility ◽  
Different Doses

The new triazole derivative SCH 56592 has been tested in a National Committee for Clinical Laboratory Standards-adapted in vitro susceptibility test, and its activity against 12 isolates of Blastomyces dermatitidis yeast-like forms has been compared with those of amphotericin B, itraconazole, and fluconazole. SCH 56592 was the most active of the four compounds, with an MIC at which 90% of the isolates are inhibited of 0.06 microgram/ml and a minimal fungicidal concentration at which 90% of the isolates are inhibited of 4 micrograms/ml. The results of the treatment of mice infected with B. dermatitidis with three different doses of SCH 56592 (25, 5, or 1 mg/kg of body weight), amphotericin B (1 mg/kg), or itraconazole (150 mg/kg) confirmed the potent activity of SCH 56592. Survival was prolonged at each dose of SCH 56592, and sterilization of the lungs occurred in the high-dose group but not in the groups treated with itraconazole or fluconazole. SCH 56592 is a promising new azole antifungal drug that should be studied in humans with blastomycosis.

scholarly journals In Vitro Evaluation of Double and Triple Combinations of Antifungal Drugs against Aspergillus fumigatus and Aspergillus terreus

2004 ◽  
Vol 48 (3) ◽  
pp. 970-978 ◽  
Author(s):  
Eric Dannaoui ◽  
Olivier Lortholary ◽  
Françoise Dromer
Keyword(s):  
Aspergillus Fumigatus ◽  
Amphotericin B ◽  
Clinical Laboratory ◽  
Antifungal Drugs ◽  
National Committee ◽  
In Vitro Tests ◽  
Triple Combination ◽  
Reading Technique

ABSTRACT Microdilution broth checkerboard techniques based on the National Committee for Clinical Laboratory Standards methodology were used to study double and triple antifungal combinations against clinical isolates of Aspergillus fumigatus and A. terreus. The influences of the end-point definition (partial or complete inhibition) and the mode of reading (visually or spectrophotometrically) were determined. Interactions between antifungal drugs were also evaluated by agar diffusion tests. Combinations of caspofungin with either amphotericin B or voriconazole were additive for all the isolates, and antagonism was not observed. The interaction between caspofungin and flucytosine was synergistic for 62% of the isolates. In contrast, the interaction between voriconazole and flucytosine was never synergistic and antagonism was noted for 93% of the isolates. The triple combination of caspofungin with flucytosine and amphotericin B was synergistic for all the isolates tested. The triple combination of caspofungin with flucytosine and voriconazole was also mostly synergistic; but complex interactions were obtained for some isolates, with synergy or antagonism depending on the concentrations of caspofungin and voriconazole. Analysis of the influence of the reading technique on the results showed that spectrophotometric reading was a good alternative to the recommended visual reading. The results of these in vitro tests suggest that the activity of flucytosine as part of a double combination with caspofungin and as part of a triple combination with caspofungin and amphotericin B against Aspergillus spp. warrants further investigations. Animal studies are needed to evaluate the in vivo efficacies of these combinations.

Use of spectrophotometric reading for in vitro antifungal susceptibility testing ofAspergillusspp.

1999 ◽  
Vol 45 (10) ◽  
pp. 871-874 ◽  
Author(s):  
Eric Dannaoui ◽  
Florence Persat ◽  
Marie-France Monier ◽  
Elisabeth Borel ◽  
Marie-Antoinette Piens ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Antifungal Susceptibility ◽  
Reference Method ◽  
Antifungal Susceptibility Testing ◽  
Aspergillus Species ◽  
National Committee ◽  
Broth Microdilution Method

A comparative study of visual and spectrophotometric MIC endpoint determinations for antifungal susceptibility testing of Aspergillus species was performed. A broth microdilution method adapted from the National Committee for Clinical Laboratory Standards (NCCLS) was used for susceptibility testing of 180 clinical isolates of Aspergillus species against amphotericin B and itraconazole. MICs were determined visually and spectrophotometrically at 490 nm after 24, 48, and 72h of incubation, and MIC pairs were compared. The agreement between the two methods was 99% for amphotericin B and ranged from 95 to 98% for itraconazole. It is concluded that spectrophotometric MIC endpoint determination is a valuable alternative to the visual reference method for susceptibility testing of Aspergillus species.Key words: antifungal, susceptibility testing, Aspergillus, spectrophotometric reading.

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