Efficacy of micafungin alone or in combination against systemic murine aspergillosis

We tested the efficacy of micafungin (FK) alone or in combination with other antifungals against systemic murine aspergillosis. FK alone at 10 mg/kg of body weight/dose prolonged survival (P = 0.01) and reduced CFU in the brain and kidney. Combination therapy that used suboptimal FK with amphotericin B or itraconazole prolonged survival. Although no survivors were free of infection, no antagonism was seen. Nikkomycin Z with FK showed significantly greater potency (P < 0.01) than either alone.     

Efficacy of ravuconazole (BMS-207147) in a guinea pig model of disseminated aspergillosis

Ravuconazole (BMS-207147, ER-30346), an oral triazole, was evaluated in an immunosuppressed temporarily neutropenic guinea pig model of invasive aspergillosis. In this model, guinea pigs were immunosuppressed with triamcinolone 20 mg/kg sc od beginning 4 days before challenge and made neutropenic with cyclophosphamide 300 mg/kg ip 1 day before challenge. Treatments of ravuconazole 5, 10 and 25 mg/kg po od were compared with itraconazole 2.5 and 5.0 mg/kg po bd and amphotericin B 1.25 mg/kg ip od. Treatment began 24 h after lethal intravenous challenge with Aspergillus fumigatus and continued for 5 days. Mortality occurred in eight of eight untreated control animals versus none of eight treated with ravuconazole 5 or 10 mg/kg/day or itraconazole 10 mg/kg/day. Mortality occurred in one of eight animals treated with ravuconazole 25 mg/kg/day, one of eight with amphotericin B and two of eight treated with itraconazole 5 mg/kg/day. Compared with controls, each of the antifungals examined significantly reduced the tissue burden in liver and brain, although only the highest doses of the azole drugs and amphotericin B significantly reduced tissue burden in the kidney. All three doses of ravuconazole improved survival and also reduced the tissue burden of ASPERGILLUS: In this model of invasive aspergillosis, ravuconazole showed significant activity and may be a useful compound in human disease.     

Efficacy of FK463, a new lipopeptide antifungal agent, in mouse models of disseminated candidiasis and aspergillosis

The efficacy of intravenous injection of FK463, a novel water-soluble lipopeptide, was evaluated in mouse models of disseminated candidiasis and aspergillosis and was compared with those of fluconazole (FLCZ) and amphotericin B (AMPH-B). In the candidiasis model, FK463 significantly prolonged the survival of intravenously infected mice at doses of 0.125 mg/kg of body weight or higher. In disseminated candidiasis caused by Candida species, including FLCZ-resistant Candida albicans, FK463 exhibited an efficacy 1.4 to 18 times inferior to that of AMPH-B, with 50% effective doses (ED(50)s) ranging from 0.21 to 1.00 mg/kg and 0.06 to 0.26 mg/kg, respectively, and was much more active than FLCZ. The protective effect of FK463 was not obviously influenced by the fungal inoculum size, the starting time of the treatment, or the immunosuppressed status of the host. The reduction in efficacy was less than that observed with FLCZ or AMPH-B. The efficacy of FK463 was also evaluated in the disseminated candidiasis target organ assay and was compared with those of FLCZ and AMPH-B. Efficacies were evaluated on the basis of a comparison between the mean log(10) CFU in kidneys in the groups treated with antifungal agents and that in control group. A single dose of FK463 at 0.5 mg/kg or higher significantly reduced the viable counts in kidneys compared with the numbers of yeast cells before treatment, and its efficacy was comparable to that of AMPH-B, while FLCZ at 4 mg/kg showed only a suppressive effect on the growth of C. albicans in the kidneys. In the disseminated aspergillosis model, FK463 given at doses of 0.5 mg/kg or higher significantly prolonged the survival of mice infected intravenously with Aspergillus fumigatus conidia. The efficacy of FK463 was about 2 times inferior to that of AMPH-B, with ED(50)s ranging from 0.25 to 0.50 mg/kg and 0.11 to 0.29 mg/kg, respectively. These results indicate that FK463 may be a potent parenterally administered therapeutic agent for disseminated candidiasis and aspergillosis.     

In-vitro susceptibility of Aspergillus spp. isolates to amphotericin B and itraconazole

The MICs of amphotericin B and itraconazole for 230 isolates of Aspergillus spp., comprising 156 Aspergillus fumigatus, 20 Aspergillus terreus, 22 Aspergillus flavus, 17 Aspergillus nidulans and 15 Aspergillus niger, were determined by a broth microdilution method with RPMI 1640 medium. No isolate was detected with an MIC of amphotericin B >2 mg/L. Itraconazole MICs >16 mg/L were detected for four Aspergillus fumigatus and one Aspergillus nidulans isolates.     

Efficacy of amphotericin B or itraconazole in a murine model of central nervous system Aspergillus infection

Given the greater than 90% lethality of clinical central nervous system (CNS) aspergillosis despite current therapies, there is a need for an animal model to study therapeutic strategies. We previously established a model of CNS aspergillosis by intracerebral infection and report here the results of treatment with the two therapies with the greatest clinical experience, i.e., treatments with amphotericin B (AMB) and itraconazole (ITZ). Mice were given cyclophosphamide to produce pancytopenia. AMB was given intraperitoneally (i.p.; 3 mg/kg of body weight) or intravenously (i.v.; 0.8 mg/kg) once daily. ITZ in cyclodextrin was given by gavage once daily at a dose of 100 mg/kg or twice daily at 50 mg/kg. Treatments were started at day 1 postinfection and given for 10 days. At day 15, survivors were euthanatized. Ninety percent of the mice given no treatment died by day 6, and 100% died by day 10. Mice treated with AMB either i.p. or i.v. had 40% survival. Mice treated with ITZ either once or twice per day had a median survival time of 10 days, compared with 4 days for control animals, but a survival rate of only 10%. AMB and ITZ prolonged survival (P, <0.0001 to <0.05) compared with controls. Brains from surviving mice had CFU of Aspergillus fumigatus. This model can be used to compare newer antifungals and to study combination therapy or immunotherapy to find better therapeutic alternatives.     

Efficacy of Abelcet alone, or in combination therapy, against experimental central nervous system aspergillosis

BACKGROUND: CNS aspergillosis is the most frequent and devastating manifestation of dissemination and mortality is high. METHODS: Cyclophosphamide-suppressed CD-1 mice were infected intracerebrally with conidia of Aspergillus fumigatus and treated for 10 days with suboptimal doses of Abelcet (4 mg/kg) plus micafungin (1 mg/kg), caspofungin (1 mg/kg), itraconazole (100 mg/kg) or voriconazole (40 mg/kg) and compared with monotherapy. Other groups included conventional amphotericin B (1 mg/kg), Abelcet at 10 or 12 mg/kg or 5% dextrose water (diluent control). RESULTS: All controls died and all treatment regimens significantly prolonged survival. No monotherapy regimen was superior to another. All dosages of Abelcet and conventional amphotericin B tested were equivalent. Significant enhancement of survival over the respective monotherapies was found only with the combination of Abelcet and voriconazole. Other combinations were not better than Abelcet alone. Recovery of cfu from the brains and kidneys of survivors showed that no regimen was curative. Abelcet and voriconazole showed significantly enhanced efficacy in reducing brain infection. Other combinations showed lower cfu, but no significant enhancement over either drug alone. Dose-escalation of Abelcet alone did not increase reduction of cfu. Recovery from the kidneys showed non-significant reduction of cfu by combinations compared with monotherapies. CONCLUSIONS: Each of the drugs tested had significant efficacy against CNS aspergillosis and Abelcet in combination with voriconazole had enhanced efficacy. Additional studies are warranted.     

Comparative antifungal activities and plasma pharmacokinetics of micafungin (FK463) against disseminated candidiasis and invasive pulmonary aspergillosis in persistently neutropenic rabbits

Micafungin (FK463) is an echinocandin that demonstrates potent in vitro antifungal activities against Candida and Aspergillus species. However, little is known about its comparative antifungal activities in persistently neutropenic hosts. We therefore investigated the plasma micafungin pharmacokinetics and antifungal activities of micafungin against experimental disseminated candidiasis and invasive pulmonary aspergillosis in persistently neutropenic rabbits. The groups with disseminated candidiasis studied consisted of untreated controls (UCs); rabbits treated with desoxycholate amphotericin B (DAMB) at 1 mg/kg of body weight/day; or rabbits treated with micafungin at 0.25, 0.5, 1, and 2 mg/kg/day intravenously. Compared with the UCs, rabbits treated with micafungin or DAMB showed significant dosage-dependent clearance of Candida albicans from the liver, spleen, kidney, brain, eye, lung, and vena cava. These in vivo findings correlated with the results of in vitro time-kill assays that demonstrated that micafungin has concentration-dependent fungicidal activity. The groups with invasive pulmonary aspergillosis studied consisted of UCs; rabbits treated with DAMB; rabbits treated with liposomal amphotericin B (LAMB) at 5 mg/kg/day; and rabbits treated with micafungin at 0.5, 1, and 2 mg/kg/day. In comparison to the significant micafungin dosage-dependent reduction of the residual burden (in log CFU per gram) of C. albicans in tissue, micafungin-treated rabbits with invasive pulmonary aspergillosis had no reduction in the concentration of Aspergillus fumigatus in tissue. DAMB and LAMB significantly reduced the burdens of C. albicans and A. fumigatus in tissues (P < 0.01). Persistent galactomannan antigenemia in micafungin-treated rabbits correlated with the presence of an elevated burden of A. fumigatus in pulmonary tissue. By comparison, DAMB- and LAMB-treated animals had significantly reduced circulating galactomannan antigen levels. Despite a lack of clearance of A. fumigatus from the lungs, there was a significant improvement in the rate of survival (P < 0.001) and a reduction in the level of pulmonary infarction (P < 0.05) in micafungin-treated rabbits. In summary, micafungin demonstrated concentration-dependent and dosage-dependent clearance of C. albicans from persistently neutropenic rabbits with disseminated candidiasis but not of A. fumigatus from persistently neutropenic rabbits with invasive pulmonary aspergillosis.     

In vitro activities of three licensed antifungal agents against spanish clinical isolates of Aspergillus spp

The aim of the present study was to identify retrospectively trends in the species distributions and the susceptibility patterns of Aspergillus species causing fungal infections in Spanish medical centers from 2000 to 2002. The susceptibilities of 338 isolates to amphotericin B, itraconazole, and voriconazole were tested. Aspergillus fumigatus was the most common species (54.7%), followed by Aspergillus terreus (14.8%) and Aspergillus flavus (13.9%). Non-A. fumigatus species were encountered in 45.3% of the samples studied. The majority of Aspergillus isolates were obtained from respiratory tract specimens, followed by ear and skin samples. The geometric mean (GM) MIC of amphotericin B was 0.56 micro g/ml, and the amphotericin B MIC was >2 micro g/ml for 16 isolates (4.7%). Nine of them were A. terreus. The GM MIC of itraconazole was 0.37, and the itraconazole MIC was >4 micro g/ml for 12 (3.5%) isolates. The voriconazole MICs were also high for 8 of the 12 strains for which itraconazole MICs were high (voriconazole MIC range, 2 to 8 micro g/ml).     

In vitro interaction of terbinafine with itraconazole,fluconazole, amphotericin B and 5-flucytosine against Aspergillus spp

We investigated the in vitro interaction of terbinafine with itraconazole, fluconazole, amphotericin B and 5-flucytosine, against Aspergillus spp. We tested three isolates of Aspergillus fumigatus (one resistant to itraconazole), and two each of Aspergillus flavus, Aspergillus niger and Aspergillus terreus. We employed a broth microdilution-based method derived from an in vivo validated method capable of detecting itraconazole resistance in A. fumigatus. We studied the effect on the MICs by calculation of the fractional inhibitory concentration (FIC) and fractional fungicidal concentration (FFC) (99.99% kill). Itraconazole and terbinafine were synergic or additive in all strains (FIC = 0.15-1.0). Fluconazole and terbinafine were synergic with A. fumigatus, A. terreus and A. flavus (FIC = 0.3-0.5) and indifferent with A. niger (FIC = 2) isolates. Amphotericin B and terbinafine were mostly indifferent or antagonistic (FIC = 1.0-4.02). Flucytosine and terbinafine were usually indifferent or antagonistic (FIC = 0.63-8.5). FFCs were generally in accord with FICs. The use of terbinafine in combination therapy for Aspergillus infections with azoles seems promising, whereas terbinafine and amphotericin B or flucytosine in combination were less effective.     

Acquired itraconazole resistance in Aspergillus fumigatus

The antifungal susceptibility profiles of four ASPERGILLUS: fumigatus isolates, recovered at different times from a patient treated with itraconazole for a pulmonary ASPERGILLUS: infection, were evaluated. Itraconazole MICs against two pre-treatment isolates were 0.5 mg/L, whilst two later isolates, recovered after at least 4 months of itraconazole therapy, had itraconazole MICs of >16 mg/L. In vivo susceptibilities to itraconazole and amphotericin B were tested in a murine model of disseminated aspergillosis. Treatment efficacy was evaluated by examining mortality rates and qualitative cultures of brain and kidneys. Itraconazole therapy significantly prolonged survival of mice infected with the initial isolates as compared with untreated controls. The third isolate was only partially susceptible to itraconazole in vivo, and the fourth isolate was highly resistant. The four isolates were typed by random amplified polymorphic DNA (RAPD) with four different primers. RAPD patterns obtained with each of them were identical, suggesting that the same strain was recovered over time and had acquired resistance to itraconazole.     

Efficacy of intravenous itraconazole against experimental pulmonary aspergillosis.

The efficacy of intravenous itraconazole solubilized in hydroxypropyl-beta-cyclodextrin was assessed in a rat model of Aspergillus fumigatus pneumonia. Immunosuppressed rats were infected by intratracheal inoculation of A. fumigatus conidia. Intravenous administration of various doses of itraconazole was started immediately after infection and continued once a day for 7 days. A 10-mg dose of intravenous itraconazole per kg was as effective on survival as 1 mg of amphotericin B per kg daily (a survival rate of 100% in 28 days), while treatment with 1 mg/kg did not increase the survival rate. The 50% lethal dose of intravenous itraconazole given to immunosuppressed and uninfected rats for 7 days was 24.5 mg/kg/day. A microbiological assay to estimate accumulation in tissue after five daily intravenous administrations of itraconazole at 10 mg/kg showed that itraconazole and its active metabolites were present in the lungs for at least 6 h, reaching the MIC as previously described (B. Dupont and E. Drouchet, Rev. Infect. Dis. 9(Suppl. 1):71-76, 1987; A. Espinel-Ingroff, S. Shadomy, and R. J. Gebhart, Antimicrob. Agents Chemother. 26:5-9, 1984). Intravenous itraconazole was considered to be worth evaluating in clinical trials of aspergillosis.     

Efficacy of SCH-56592 in a temporarily neutropenic murine model of invasive aspergillosis with an itraconazole-susceptible and an itraconazole-resistant isolate of Aspergillus fumigatus.

SCH-56592 (SCH) is a novel triazole antifungal agent with excellent in vitro activity against Aspergillus. We compared three doses (5, 10, and 25 mg/kg of body weight) of SCH with itraconazole (ITZ; 25 mg/kg) and amphotericin B (AB; 5 mg/kg) in a temporarily neutropenic murine model of disseminated aspergillosis (lungs and kidneys) against one ITZ-susceptible (AF71) and one ITZ-resistant (AF90) isolate of Aspergillus fumigatus. Treatment started 24 h after infection and lasted for 10 days. Dosing regimens for SCH were once daily for 10 days, those for ITZ were three times daily for 2 days and then twice daily for 3 to 10 days, and those for AB were once daily on days 1, 2, 4, and 7. Both isolates killed 90% of control mice. Kidneys and lungs from survivors were cultured on day 11. Against AF71, all three doses of SCH and ITZ yielded a 90 to 100% survival rate and AB yielded 40% survival (P < or = 0.01 to 0.0001 for all treatment groups compared with the controls). All three doses of SCH were superior to AB in cultures of lung and kidney tissue samples (P < or = 0.01 to 0.0002) and SCH at 25 mg/kg was superior to ITZ in cultures of kidneys (P = 0.01). Against AF90, the highest dose of SCH (25 mg/kg) resulted in a 100% survival rate, compared with 60 and 20% survival rates for the groups treated with SCH at 10 and 5 mg/kg, respectively. Treatment with ITZ yielded no survivors. AB therapy achieved a 50% survival rate. SCH at 25 mg/kg (P < 0.001), SCH at 10 mg/kg (P < or = 0.005), and AB (P < 0.05) were superior to ITZ in cultures of lungs and kidneys. There was a correlation between the MICs of SCH and quantitative organ culture results and between the minimum fungicidal concentration of AB with quantitative organ culture results. SCH appears to be a highly effective anti-Aspergillus compound in this model. There appears to be a degree of cross-resistance between itraconazole and SCH.     

Efficacy of aerosolized amphotericin B desoxycholate and liposomal amphotericin B in the treatment of invasive pulmonary aspergillosis in severely immunocompromised rats.

The effects of treatment with aerosolized amphotericin B desoxycholate and aerosolized liposomal amphotericin B were evaluated in severely immunosuppressed rats with invasive pulmonary aspergillosis. Aerosol treatment with amphotericin B desoxycholate consisted of a single dose (60 min) with amphotericin B concentrations in the nebulizer reservoir of 1, 2 and 4 mg/mL, respectively. For liposomal amphotericin B, aerosol treatment consisted of single, double or quadruple doses with a nebulizer reservoir concentration of 4 mg/mL of amphotericin B. Treatment, started at 30 h after inoculation, with aerosolized amphotericin B desoxycholate (nebulizer reservoir concentration 2 mg/mL) significantly prolonged survival of rats as compared with placebo-treated rats, whereas treatment with aerosolized amphotericin B desoxycholate with nebulizer reservoir concentration of 1 or 4 mg/mL did not have a significant effect on survival. Treatment with aerosolized liposomal amphotericin B significantly prolonged survival with all treatment regimens when compared with placebo-treated animals. Aerosol treatment did not prevent dissemination of the infection. The effects of amphotericin B desoxycholate and liposomal amphotericin B on pulmonary surfactant function were also evaluated in vitro. Amphotericin B desoxycholate inhibited surfactant function in a dose-dependent fashion. Liposomal amphotericin B had no detrimental effect on surface activity of surfactant. These results indicate that aerosol administration of amphotericin B, especially the liposomal formulation, could be an additional approach to optimizing treatment of invasive pulmonary aspergillosis.     

Efficacy of FK463, a new lipopeptide antifungal agent, in mouse models of pulmonary aspergillosis

The efficacy of FK463, a novel water-soluble lipopeptide, was evaluated in mouse models of pulmonary aspergillosis and was compared with that of amphotericin B (AMPH-B). In the pulmonary aspergillosis models induced by intranasal inoculation, FK463 exhibited good efficacy, with 50% effective doses in the range of 0. 26 to 0.51 mg/kg of body weight; these values were comparable to those of AMPH-B. In an Aspergillus target organ assay with immunosuppressed mice, under conditions of constant plasma levels of FK463, using a subcutaneously implanted osmotic pressure pump, a significant reduction in viable fungal cells was observed at plasma FK463 levels of 0.55 to 0.80 microgram/ml or higher. We conclude that FK463 is highly effective in the treatment of pulmonary aspergillosis in this animal model. These results indicate that FK463 may be a potent parenterally administered antifungal agent for pulmonary aspergillosis.     

Comparative studies on the efficacy of AmBisome and Fungizone in a mouse model of disseminated aspergillosis

OBJECTIVES: The efficacy of intravenous injections of a liposomal formulation of amphotericin B (AmBisome) and amphotericin B deoxycholate (Fungizone) was evaluated in immunocompetent and temporarily leucopenic mouse models of disseminated aspergillosis using seven isolates of Aspergillus. METHODS: Mice were infected with the organisms via tail veins. At 4 h after infection, antifungals were administered intravenously. For 30 days the number of mice surviving was recorded. RESULTS: AmBisome at 1 mg/kg or higher significantly prolonged the survival time of mice infected with five out of seven isolates of Aspergillus compared with the control group. There was no difference in in vivo activity between AmBisome and Fungizone at 1 mg/kg in six isolates of Aspergillus. At the maximum tolerated dose of antifungals, however, AmBisome (10 mg/kg) showed greater efficacy than Fungizone (1 mg/kg). CONCLUSIONS: These results suggest that the overall protective activity of AmBisome against disseminated aspergillosis is superior to that of Fungizone.     

In vitro activity of the new triazole BMS-207147 against Aspergillus species in comparison with itraconazole and amphotericin B

The in vitro activity of BMS-207147 against 80 clinical isolates of Aspergillus was compared with that of itraconazole and amphotericin B, using a validated microtiter method. Geometric mean MICs (in microg/ml) were as follows: 1.71 for BMS-207147, 0.67 for itraconazole, and 0.63 for amphotericin B. The range of concentrations of each drug was 0.125 to >16 microg/ml. Aspergillus fumigatus was significantly more susceptible to BMS-207147 (P < 0. 05) than A. terreus and A. flavus. No BMS-207147-resistant A. fumigatus isolates were identified, though eight itraconazole-resistant (MIC, >8 microg/ml) isolates were. BMS-207147 is active against Aspergillus spp. at slightly high concentrations compared with itraconazole and amphotericin B.     

Effect of amphotericin B and micafungin combination on survival, histopathology, and fungal burden in experimental aspergillosis in the p47phox-/- mouse model of chronic granulomatous disease

Chronic granulomatous disease (CGD) is an inherited disorder of the NADPH oxidase characterized by recurrent life-threatening bacterial and fungal infections. We characterized the effects of single and combination antifungal therapy on survival, histopathology, and laboratory markers of fungal burden in experimental aspergillosis in the p47phox-/- knockout mouse model of CGD. CGD mice were highly susceptible to intratracheal Aspergillus fumigatus challenge, whereas wild-type mice were resistant. CGD mice were challenged intratracheally with a lethal inoculum (1.25 x 10(4) CFU/mouse) of A. fumigatus and received one of the following regimens daily from day 0 to 4 after challenge (n = 19 to 20 per treatment group): (i) vehicle, (ii) amphotericin B (intraperitoneal; 1 mg/kg of body weight), (iii) micafungin (intravenous; 10 mg/kg), or (iv) amphotericin B plus micafungin. The rank order of therapeutic efficacy based on prolonged survival, from highest to lowest, was as follows: amphotericin B plus micafungin, amphotericin B alone, micafungin alone, and the vehicle. Lung histology showed pyogranulomatous lesions and invasive hyphae, but without hyphal angioinvasion or coagulative necrosis. Treatment with micafungin alone or combined with amphotericin B produced swelling of invasive hyphae that was not present in mice treated with the vehicle or amphotericin B alone. Assessment of lung fungal burden by quantitative PCR showed no significant difference between treatment groups. Serum galactomannan levels were at background despite documentation of invasive aspergillosis by histology. Our findings showed the superior efficacy of the amphotericin B and micafungin combination compared to either agent alone after A. fumigatus challenge and also demonstrated unique features of CGD mice as a model for experimental aspergillosis.     

Pharmacodynamic effects of simulated standard doses of antifungal drugs against Aspergillus species in a new in vitro pharmacokinetic/pharmacodynamic model

In conventional ΜΙC tests, fungi are exposed to constant drug concentrations, whereas in vivo, fungi are exposed to changing drug concentrations. Therefore, we developed a new in vitro pharmacokinetic/pharmacodynamic model where human plasma pharmacokinetics of standard doses of 1 mg/kg amphotericin B, 4 mg/kg voriconazole, and 1 mg/kg caspofungin were simulated and their pharmacodynamic characteristics were determined against three clinical isolates of Aspergillus fumigatus, Aspergillus flavus, and Aspergillus terreus with identical MICs (1 mg/liter for amphotericin B, 0.5 mg/liter for voriconazole) and minimum effective concentrations (0.5 mg/liter for caspofungin). This new model consists of an internal compartment (a 10-ml dialysis tube made out of a semipermeable cellulose membrane allowing the free diffusion of antifungals but not galactomannan) inoculated with Aspergillus conidia and placed inside an external compartment (a 700-ml glass beaker) whose content is diluted after the addition of antifungal drugs by a peristaltic pump at the same rate as the clearance of the antifungal drugs in human plasma. Fungal growth was assessed by galactomannan production. Despite demonstrating the same MICs, amphotericin B completely inhibited (100%) A. fumigatus but not A. flavus and A. terreus, whose growth was delayed for 7.53 and 22.8 h, respectively. Voriconazole partially inhibited A. fumigatus (49.5%) and Α. flavus (27.9%) but not Α. terreus; it delayed their growth by 3.99 h (A. fumigatus) and 5.37 h (Α. terreus). Caspofungin did not alter galactomannan production in all of the species but A. terreus. The new model simulated human pharmacokinetics of antifungal drugs and revealed important pharmacodynamic differences in their activity.     

In vitro pharmacodynamics of amphotericin B, itraconazole, and voriconazole against Aspergillus, Fusarium, and Scedosporium spp

We compared the in vitro pharmacodynamics of amphotericin B, itraconazole, and voriconazole against Aspergillus, Fusarium, and Scedosporium species with a combination of two non-culture-based techniques: the tetrazolium salt 2,3-bis-(2-methoxy-4-nitro-5-[(sulfenylamino)carbonyl]-2H-tetrazolium-hydroxide) (XTT) colorimetric reduction assay, and fluorescent microscopy with the cellular morbidity dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC) to directly visualize hyphal damage. Amphotericin B exhibited species-specific concentration-dependent activity, with 50% effective concentrations (EC(50)s) ranging from 0.10 to 0.12 mg/ml for A. fumigatus, 0.36 to 0.53 mg/ml for A. terreus, 0.27 to > or = 32 mg/ml for F. solani, 0.41 to 0.55 mg/ml for F. oxysporum, and 0.97 and 0.65 mg/ml for S. apiospermum and S. prolificans, respectively. Similarly, itraconazole inhibited the growth of A. fumigatus and A. terreus isolates with MICs of <1 mg/ml (EC(50) 0.03 to 0.85 mg/ml) and S. apiospermum, but was not active against Fusarium species or S. prolificans. Voriconazole effectively inhibited the growth of Aspergillus, Fusarium, and S. apiospermum (EC(50) 0.10 to 3.3 mg/ml) but had minimal activity against a multidrug-resistant isolate of F. solani or S. prolificans. Hyphal damage visualized by DiBAC staining was observed more frequently with voriconazole and amphotericin B versus itraconazole. These data highlight the species-specific differences in antifungal pharmacodynamics between mold-active agents that could be relevant for the development of in vitro susceptibility breakpoints and antifungal dosing in vivo.     

Dose Range Evaluation of Liposomal Nystatin and Comparisons with Amphotericin B and Amphotericin B Lipid Complex in Temporarily Neutropenic Mice Infected with an Isolate of Aspergillus fumigatus with Reduced Susceptibility to Amphotericin B

Using an isolate of Aspergillus fumigatus that is less susceptible in vivo to amphotericin B than most other isolates, we compared different doses of liposomal nystatin (L-nystatin), liposomal amphotericin B (L-amphotericin), and amphotericin B lipid complex (ABLC) with amphotericin B deoxycholate. Four experiments with intravenously infected neutropenic mice were conducted. A dose of L-nystatin at 10 mg/kg of body weight was toxic (the mice had fits or respiratory arrest). The optimal dosage of L-nystatin was 5 mg/kg daily on days 1, 2, 4, and 7 (90% survival). This was superior to L-amphotericin (5 mg/kg [P = 0.24] and 1 mg/kg [P < 0.0001]), ABLC (5 mg/kg [P = 0.014] and 1 mg/kg [P < 0.0001]), and amphotericin B deoxycholate (5 mg/kg [P = 0.008]). In terms of liver and kidney cultures, L-nystatin (5 mg/kg) was superior to all other regimens (P = 0.0032 and <0.0001, respectively). Higher doses of L-amphotericin (25 and 50 mg/kg) in one earlier experiment were more effective (100% survival) than 1 mg of L-amphotericin per kg and amphotericin deoxycholate (5 mg/kg) in terms of mortality and both liver and kidney culture results and to L-amphotericin (5 mg/kg) in terms of liver and kidney culture results only. ABLC (25 mg/kg) given daily for 7 days was superior to ABLC (50 mg/kg [P = 0.03]) but not to ABLC at 5 mg/kg or amphotericin B deoxycholate in terms of mortality, although it was in terms of liver and kidney culture results. No dose-response for amphotericin B (5 and 1 mg/kg) was demonstrable. In conclusion, in this stringent model, high doses of L-amphotericin and ABLC could overcome reduced susceptibility to amphotericin B deoxycholate, but all were inferior to 5- to 10-fold lower doses of L-nystatin.