Caspofungin (Merck Pharmaceuticals) was tested in vitro against 25 clinical isolates of Coccidoides immitis. In vitro susceptibility testing was performed in accordance with the National Committee for Clinical Laboratory Standards document M38-P guidelines. Two C. immitis isolates for which the caspofungin MICs were different were selected for determination of the minimum effective concentration (MEC), and these same strains were used for animal studies. Survival and tissue burdens of the spleens, livers, and lungs were used as antifungal response markers. Mice infected with strain 98-449 (48-h MIC, 8 μg/ml; 48-h MEC, 0.125 μg/ml) showed 100% survival to day 50 when treated with caspofungin at ≥1 mg/kg. Mice infected with strain 98-571 (48-h MIC, 64 μg/ml; 48-h MEC, 0.125 μg/ml) displayed ≥80% survival when the treatment was caspofungin at ≥5 mg/kg. Treatment with caspofungin at 0.5, 1, 5, or 10 mg/kg was effective in reducing the tissue fungal burdens of mice infected with either isolate. When tissue fungal burden study results were compared between strains, caspofungin showed no statistically significant difference in efficacy in the organs of the mice treated with both strains. A better in vitro-in vivo correlation was noted when we used the MEC instead of the MIC as the endpoint for antifungal susceptibility testing. Caspofungin may have a role in the treatment of coccidioidomycosis.
Caspofungin is a potent antifungal inhibiting glucan synthesis in Candida species. However, caspofungin is not 100% curative in candidiasis. Therefore, we evaluated combinations of fluconazole with caspofungin for murine candidemia. We could not show any benefit of combined therapy over individual antifungal drugs.
Weanling outbred rats were infected with Cryptococcus neoformans by direct percranial puncture and inoculation into the cranium. A lethal infection ensued. Treatment with LY295337, a depsipeptide with antifungal activity, was effective in prolonging survival and reducing fungal counts in brain tissue. Weanling rats are an acceptable model for the study of central nervous system infection with C. neoformans.
The activities of anidulafungin and caspofungin against Candida glabrata were evaluated. MICs, 50% inhibitory concentrations (IC50 values), and IC90 values for anidulafungin were lower than those for caspofungin for 16 of 18 strains tested. Anidulafungin has potent in vitro activity against C. glabrata that is maintained against isolates with elevated caspofungin MICs.
Immunosuppressed mice were infected intravenously with conidia of Scedosporium prolificans. Treatment was begun 1 day later with liposomal amphotericin B, caspofungin, or both drugs initiated concurrently. Amphotericin B and caspofungin were each effective, but combined therapy did not appear to offer advantages over liposomal amphotericin B alone.
A patient with azole-refractory thrush-esophagitis responded initially to caspofungin, but the treatment eventually failed. In a murine model, caspofungin was effective against two early isolates for which the MICs of caspofungin were low, but it was less effective against a late isolate for which the MIC of caspofungin was greater. We concluded that there is a correlation between in vivo failure and rising in vitro caspofungin MICs.
Posaconazole and/or amphotericin B was given to mice pretreated with a steroid and then infected by inhalation of Aspergillus flavus conidia. Two laboratories conducted studies using almost identical protocols to evaluate both survival and lung tissue burdens 8 days after infection. The results of the in vivo studies performed at both laboratories were consistent. We found that (i) up to 5 mg of amphotericin B per kg of body weight was poorly effective in treating invasive aspergillosis; (ii) posaconazole at 2 or 10 mg/kg/dose prolonged survival and reduced lung tissue CFU; and (iii) there was generally no antagonistic interaction of the drugs in combination, even when the experiments were designed to maximize the likelihood of antagonism. These studies do not confirm the antagonistic interaction of triazoles and polyenes reported by others.
Most manifestations of candidiasis are associated with biofilm formation on biological or inanimate surfaces. Candida albicans biofilms are recalcitrant to treatment with conventional antifungal therapies. Here we report on the activity of caspofungin, a new semisynthetic echinocandin, against C. albicans biofilms. Caspofungin displayed potent in vitro activity against sessile C. albicans cells within biofilms, with MICs at which 50% of the sessile cells were inhibited well within the drug's therapeutic range. Scanning electron microscopy and confocal scanning laser microscopy were used to visualize the effects of caspofungin on preformed C. albicans biofilms, and the results indicated that caspofungin affected the cellular morphology and the metabolic status of cells within the biofilms. The coating of biomaterials with caspofungin had an inhibitory effect on subsequent biofilm development by C. albicans. Together these findings indicate that caspofungin displays potent activity against C. albicans biofilms in vitro and merits further investigation for the treatment of biofilm-associated infections.
The in vivo activities of posaconazole, itraconazole, and amphotericin B in neutropenic mice with zygomycosis were compared. The in vitro MICs of posaconazole and itraconazole for the strains of Mucor spp. used in this study ranged from 0.125 to 8 μg/ml and 0.25 to 8 μg/ml, respectively. The in vitro MIC range for amphotericin B is 0.125 to 0.25 μg/ml. At twice-daily doses of ≥15 mg/kg of body weight, posaconazole prolonged the survival of the mice and reduced tissue burden.
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 of C. 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.
Cochleates are lipid-based supramolecular assemblies composed of natural products, negatively charged phospholipid, and a divalent cation. Cochleates can encapsulate amphotericin B (AmB), an important antifungal drug. AmB cochleates (CAMB) have a unique shape and the ability to target AmB to fungi. The minimal inhibitory concentration and the minimum lethal concentration against Candida albicans are similar to that for desoxycholate AmB (DAMB; Fungizone). In vitro, CAMB induced no hemolysis of human red blood cells at concentrations of as high as 500 μg of AmB/ml, and DAMB was highly hemolytic at 10 μg of AmB/ml. CAMB protect ICR mice infected with C. albicans when the agent is administered intraperitoneally at doses of as low as 0.1 mg/kg/day. In a tissue burden study, CAMB, DAMB, and AmBisome (liposomal AmB; LAMB) were effective in the kidneys, but in the spleen CAMB was more potent than DAMB at 1 mg/kg/day and was equivalent to LAMB at 10 mg/kg/day. In summary, CAMB are highly effective in treating murine candidiasis and compare well with AmBisome and AmB.
Ramichloridium obovoideum (“Ramichloridium makenziei”) is a rare cause of lethal cerebral phaeohyphomycosis. It has been, so far, geographically restricted to the Middle East. BALB/c mice were inoculated with two strains of R. obovoideum intracranially. Therapy with amphotericin B, itraconazole, or the investigational triazole SCH 56592 was conducted for 10 days. Half the mice were monitored for survival and half were killed for determination of the fungal load in brain tissue. Recipients of SCH 56592 had significantly prolonged survival and lower brain fungal burden, and this result was found for mice infected with both of the fungal strains tested. Itraconazole reduced the brain fungal load in mice infected with one strain but not the other, while amphotericin B had no effect on brain fungal concentrations. This study indicates a possible role of SCH 56592 in the treatment of the serious cerebral phaeohyphomycosis due to R. obovoideum.
Current therapy for leishmaniasis is unsatisfactory. Efficacious and safe oral therapy would be ideal. We examined the efficacy of SCH 56592, an investigational triazole antifungal agent, against cutaneous infection with Leishmania amazonensis and visceral infection with Leishmania donovani in BALB/c mice. Mice were infected in the ear pinna and tail with L. amazonensis promastigotes and were treated with oral SCH 56592 or intraperitoneal amphotericin B for 21 days. At doses of 60 and 30 mg/kg/day, SCH 56592 was highly efficacious in treating cutaneous disease, and at a dose of 60 mg/kg/day, it was superior to amphotericin B at a dose of 1 mg/kg/day. The means of tail lesion sizes were 0.32 ± 0.12, 0.11 ± 0.06, 0.17 ± 0.07, and 0.19 ± 0.08 mm for controls, SCH 56592 at 60 and 30 mg/kg/day, and amphotericin B recipients, respectively (P = 0.0003, 0.005, and 0.01, respectively). Parasite burden in draining lymph nodes confirmed these efficacy findings. In visceral leishmaniasis due to L. donovani infection, mice treated with SCH 56592 showed a 0.5- to 1-log-unit reduction in parasite burdens in the liver and the spleen compared to untreated mice. Amphotericin B at 1 mg/kg/day was superior to SCH 56592 in the treatment of visceral infection, with a 2-log-unit reduction in parasite burdens in both the liver and spleen. These studies indicate very good activity of SCH 56592 against cutaneous leishmaniasis due to L. amazonensis infection and, to a lesser degree, against visceral leishmaniasis due to L. donovani infection in susceptible BALB/c mice.
Sordarins are new antifungals which inhibit fungal protein synthesis by blocking elongation factor 2. Three compounds were evaluated in a murine model of histoplasmosis. Immune-competent mice were infected intravenously with 106 to 108 CFU of Histoplasma capsulatum yeast cells. Mice were treated either orally with sordarins or fluconazole from day 2 through 8 after infection or intraperitoneally with amphotericin B during the same period. Protection was measured by increased rates of survival for 30 days after infection or reduction of lung or kidney tissue counts 9 days after infection. All three of the antifungal drugs tested were protective compared with controls. Sordarins were effective at doses as low as 2 mg/kg of body weight/day. This novel class of drugs compared favorably with amphotericin B and fluconazole for the treatment of histoplasmosis.
A murine model of systemic candidiasis was used to assess the virulence of serial Candida albicans strains for which fluconazole MICs were increasing. Serial isolates from five patients with 17 episodes of oropharyngeal candidiasis were evaluated. The MICs for these isolates exhibited at least an eightfold progressive increase from susceptible (MIC < 8 μg/ml; range, 0.25 to 4 μg/ml) to resistant (MIC ≥ 16 μg/ml; range, 16 to ≥128 μg/ml). Virulence of the serial isolates from three of five patients showed a more than fivefold progressive decrease in the dose accounting for 50% mortality and was associated with development of fluconazole resistance. Low doses of fluconazole prolonged survival of mice infected with susceptible yeasts but failed to prolong survival following challenge with a resistant strain. In addition, a decreased burden of renal infection was noted in mice challenged with two of the three resistant strains. This was consistent with reduced virulence. Fluconazole did not further decrease the level of infection. In the isolates with a decrease in virulence, two exhibited overexpression of CDR, which encodes an ABC drug efflux pump. In contrast, serial isolates from the remaining two patients with the development of resistance did not demonstrate a change in virulence and fluconazole remained effective in prolonging survival, although significantly higher doses of fluconazole were required for efficacy. Resistant isolates from both of these patients exhibited overexpression of MDR. This study demonstrates that decreased virulence of serial C. albicans isolates is associated with increasing fluconazole MICs in some cases but not in others and shows that these low-virulence strains may not consistently cause infection.
Outbred ICR mice were immune suppressed either with hydrocortisone or with 5-fluorouracil and were infected intranasally with Aspergillus fumigatus. Beginning 3 days before infection some groups of mice were given recombinant human granulocyte colony-stimulating factor (G-CSF), SCH56592 (an antifungal triazole), or both. Corticosteroid-pretreated mice responded to SCH56592 and had reduced counts in lung tissue and prolonged survival. In these mice, G-CSF strongly antagonized the antifungal activity of SCH56592. Animals treated with both agents developed large lung abscesses with polymorphonuclear leukocytes and large amounts of Aspergillus. In contrast, mice made neutropenic with 5-fluorouracil and then infected with A. fumigatus conidia benefited from either G-CSF or triazoles, and the effect of the combination was additive rather than antagonistic. Host predisposing factors contribute in different ways to the outcome of growth factor therapy in aspergillosis.
Current therapy for leishmaniasis is unsatisfactory because parenteral antimonial salts and pentamidine are associated with significant toxicity and failure rates. We examined the efficacy of KY62, a new, water-soluble, polyene antifungal, against cutaneous infection with Leishmania amazonensis and against visceral infection with Leishmania donovani in susceptible BALB/c mice. Mice were infected with L. amazonensis promastigotes in the ear pinna and in the tail and were treated with KY62 or amphotericin B. The cutaneous lesions showed a remarkable response to therapy with KY62 at a dose of 30 mg per kg of body weight per day. At this dose, the efficacy of KY62 was equivalent to or better than that of amphotericin B at 1 to 5 mg/kg/day. Mice infected intravenously with 107 L. donovani promastigotes and treated with KY62 showed a 4-log reduction in the parasite burden in the liver and spleen compared to untreated mice. These studies indicate potent activity of KY62 against experimental cutaneous leishmaniasis caused by L. amazoniensis and against experimental visceral leishmaniasis caused by L. donovani.
Immune-competent ICR and BALB/c athymic (nude) mice were infected intravenously with Histoplasma capsulatum and treated with either fluconazole or nikkomycin Z or 5% dextrose (controls). In immune-competent ICR mice, fluconazole and nikkomycin Z both prolonged survival when given at 5 mg/kg of body weight twice daily. When administered in doses as low as 2.5 mg/kg twice daily, nikkomycin Z reduced fungal counts in both the spleen and liver. When both drugs were combined, there was no antagonism, and in combined therapy spleen and liver counts were reduced more than for either drug alone. However, nikkomycin Z had no effect on brain fungal burden. In nude mice fluconazole and nikkomycin Z had an additive effect in prolongation of survival and reduction of liver and spleen burden. Nikkomycin Z is well tolerated, is at least as effective as fluconazole, and may interact beneficially with fluconazole for treatment of murine histoplasmosis.
BALB/c nu/+ immunocompetent and athymic (nu/nu) mice were infected intravenously with yeast cells of Histoplasma capsulatum. Mice were either given water (controls) intraperitoneally (i.p.) or given MK-991 i.p. once daily or twice daily. Protection was measured as prolonged survival or reduction in tissue counts. MK-991 was protective in immunocompetent mice, prolonging survival and reducing counts in spleen and livers at a dose as low as 0.05 mg/kg of body weight/day. MK-991 was modestly effective in athymic mice at a higher dose, 5 mg/kg/day. These studies suggest that MK-991 may be appropriate for clinical development in histoplasmosis.
KY-62 is a water-soluble analog of amphotericin B. In vitro testing of five clinical isolates of Candida albicans showed KY-62 to have potency similar to that of amphotericin B. KY-62 was administered to mice infected intravenously with C. albicans. In vivo, KY-62 was effective in immunocompetent mice, with potency similar to that of amphotericin B. KY-62 was well tolerated up to 30 mg/kg of body weight per dose, an amount that would be lethal with amphotericin B. KY-62 was less effective in mice rendered neutropenic with 5-fluorouracil. The addition of flucytosine had little effect. KY-62 may have potential for clinical development.
Invasive fusariosis is a highly aggressive fungal infection associated with high mortality in heavily immunocompromised patients. Although posaconazole is efficacious as salvage therapy against infections caused by Fusarium species, concerns remain regarding this agent in the setting of reduced potency. To evaluate the efficacy of posaconazole as treatment or prophylaxis against invasive fusariosis caused by Fusarium solani, we utilized a neutropenic murine model of disseminated disease. ICR mice were administered escalating doses of posaconazole (6.25, 12.5, 25, or 50 mg/kg of body weight twice daily [BID]) by oral gavage beginning 2 days prior to inoculation in the prophylaxis studies or beginning 12 h after inoculation as treatment. Therapy was continued until day 9 postinoculation, and animals were monitored off therapy until day 15 for survival. Fungal burden was assessed as CFU in the kidneys. A clear dose-response relationship was observed, as the highest dose of posaconazole (50 mg/kg) was the most effective in prolonging survival and reducing tissue fungal burden both as prophylaxis and as treatment. This dose response was associated with high posaconazole serum concentrations as measured by bioassay. However, the extent of efficacy was also dependent on the infecting inoculum, as greater increases in survival and reductions in fungal burden were observed with the lower inocula tested. In this model high dosages of posaconazole were effective as treatment and prophylaxis against disseminated fusariosis caused by F. solani.
Targeted airway delivery of antifungals as prophylaxis against invasive aspergillosis may lead to high lung drug concentrations while avoiding toxicities associated with systemically administered agents. We evaluated the effectiveness of aerosolizing the intravenous formulation of voriconazole as prophylaxis against invasive pulmonary aspergillosis caused by Aspergillus fumigatus in an established murine model. Inhaled voriconazole significantly improved survival and limited the extent of invasive disease, as assessed by histopathology, compared to control and amphotericin B treatments.
Early diagnosis of invasive pulmonary aspergillosis is problematic in some patient groups due to the lack of rapid, sensitive, specific, and reliable diagnostic tests. Fungal burden and therapeutic efficacy were assessed by survival, quantitative culture (CFU counts), galactomannan enzyme immunoassay (GM-EIA), and quantitative PCR (qPCR) in a new guinea pig model of invasive pulmonary aspergillosis using an aerosol challenge. At 1 day postinfection, qPCR determined that the pulmonary fungal burden was 2 log10 higher than that determined by CFU counting and increased significantly (P < 0.03) over time. In contrast, the tissue burden assessed by CFU counting did not rise over the course of the study. Therapy with the antifungal drug voriconazole produced statistically significant decreases in pulmonary fungal burden, as detected by CFU counting (P < 0.02), qPCR, and GM-EIA (both P < 0.0002). Daily assessment of the progression of fungal infection in serum was performed by qPCR and GM-EIA. GM-EIA demonstrated a statistically significant reduction in the fungal load on days 6 and 7 in voriconazole-treated animals compared to time-matched controls (P < 0.02). Confirmation of fungal tissue burden by two or more methods should provide a more precise account of the burden, allowing improved assessment of diagnostic and therapeutic strategies in invasive pulmonary aspergillosis.
Serum (1→3)-β-d-glucan concentrations were serially measured in the presence and absence of antifungal therapy in a murine model of invasive pulmonary aspergillosis. Serum (1→3)-β-d-glucan was detected early during the course of infection, and reductions in this biomarker were associated with improved survival in animals treated with antifungal agents.
We developed a guinea pig model of cryptococcal meningitis to evaluate antifungal agents. Immunosuppressed animals challenged intracranially with Cryptococcus neoformans responded to fluconazole and voriconazole. Disease was monitored by serial cerebrospinal fluid (CSF) cultures and quantitative organ cultures. Our model produces disseminating central nervous system disease and responds to antifungal therapy.