Correlation between antifungal susceptibilities of Coccidioides immitis in vitro and antifungal treatment with caspofungin in a mouse model.

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 microg/ml; 48-h MEC, 0.125 microg/ml) showed 100% survival to day 50 when treated with caspofungin at > or =1 mg/kg. Mice infected with strain 98-571 (48-h MIC, 64 microg/ml; 48-h MEC, 0.125 microg/ml) displayed > or =80% survival when the treatment was caspofungin at > or =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.

Treatment of murine cryptococcal meningitis with UR-9751 and UR-9746.

In these studies, we compare the efficacy of two new azole antifungals with fluconazole in a murine model of cryptococcal meningitis. Mice were infected intracranially. Beginning one day later, groups of 7-10 mice were treated through to day 10 orally with UR-9751 or UR-9746 at 0.1, 0.25, 0.5, 1 or 10 mg kg(-1) day(-1) or fluconazole at 10 mg kg(-1) day(-1). At 10 mg kg(-1) day(-1), all three drugs prolonged survival over controls, but at 1 mg kg(-1) day(-1) only UR-9746 prolonged survival. Tissue counts were more varied on mice sacrificed 8 days after infection. In general, both UR drugs were equal or more potent than fluconazole, and UR-9751 was more effective than UR-9746.

Pradimicin therapy of disseminated Candida tropicalis infection in the mouse.

BMS 181184 (BMS), an analogue of pradimicin, was administered intravenously to neutropenic mice infected with either a fluconazole-susceptible or a fluconazole-resistant clinical isolate of Candida tropicalis. BMS prolonged survival at doses >3 mg kg -1 day-1, and at higher doses reduced tissue counts in mice. BMS was less potent mg for mg than amphotericin B. Combined BMS and amphotericin B were no more effective than either of the individual drugs.

Treatment of histoplasmosis with MK-991 (L-743,872).

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.

Discrepancy between in vitro and in vivo antifungal activity of albendazole.

Albendazole has in vitro activity against Cryptococcus neoformans and reduced in vitro activity for albendazole when compared with Candida albicans. The major metabolite of albendazole, albendazole sulphoxide showed no in vitro activity against isolates of either fungus. Immunocompetent mice infected intravenously (i.v.) with C. albicans were treated with albendazole doses of 20-600 mg kg-1 per day in noble agar or sesame oil for per oral (PO) administration, or 80 mg kg-1 per day in DMSO for intraperitoneal (i.p.) and i.v. administration for 10 days, and were observed for survival. Mice infected with C. neoformans intracranially received albendazole in daily doses of 600 mg kg-1 prepared in DMSO (i.p.) or peanut butter/rat chow (PO) for 10 days and were observed for survival. Mortality was not different between the treated and control animals in any study. Plasma samples from uninfected mice dosed with similar formulations and doses of albendazole were analysed by HPLC for albendazole and albendazole sulphoxide. No albendazole could be detected in any sample, while concentrations of albendazole sulphoxide (286-8697 ng ml-1) were observed in all samples. These data suggest that the absence of in vivo activity for albendazole is due to rapid conversion to the inactive albendazole sulphoxide metabolite.

Combination therapy with fluconazole and flucytosine in the murine model of cryptococcal meningitis.

This study elucidates the role of combined fluconazole and flucytosine as therapy for cryptococcosis in the murine model of meningitis. Three strains of Cryptococcus neoformans for which the range of fluconazole MICs was wide--2 microg/ml (susceptible strain), 8 microg/ml (moderately susceptible strain), and 32 microg/ml (resistant strain)--were used for infection. One day postinfection, the mice were randomized into eight treatment groups: placebo; flucytosine (40 mg/kg of body weight/day); fluconazole at 3 mg/kg/day (low dosage), 10 mg/kg/day (moderate dosage), or 20 mg/kg/day (high dosage); and combined flucytosine and fluconazole at low, moderate, or high doses of fluconazole. Three major findings were demonstrated: (i) correlation between the MICs for the isolates and the in vivo effectiveness of fluconazole as assessed by the reduction in cryptococcal brain burden, (ii) a dose-response curve (a higher dose of fluconazole was significantly more efficacious than a lower dose [P < 0.001]), and (iii) synergism between fluconazole and flucytosine (therapy with a combination of fluconazole and flucytosine was superior to therapy with either agent alone [P < 0.01]).

ZD0870 treatment of murine candidiasis caused by fluconazole resistant isolates of Candida albicans.

Mice were infected intravenously with three fluconazole susceptible and ten fluconazole resistant isolates of Candida albicans then treated with escalating doses of 0.25, 0.5, 1, 2.5, 10 and 40 mg/kg/day of the new antifungal triazole, ZD0870, for 10 days. A minimum protective dose of < 0.25 mg/kg was determined for infections introduced by the three fluconazole susceptible C. albicans and one of the fluconazole resistant isolates whereas doses ranging from 2.5 to 10 mg/kg/day were required for infections induced by seven of the resistant isolates and > or = 40 mg/kg/day for the remainder. Thus, infections caused by fluconazole resistant C. albicans may be successfully treated with ZD0870, though higher doses than those used to treat infections due to susceptible yeast may be required.

Treatment of experimental systemic mycoses with BRL 49594A.

BRL 49594A (BRL) is a water soluble analogue of amphotericin B which has been developed as a polyene with efficacy similar to amphotericin B but with much reduced toxicity. BRL was prepared in 5% glucose, and was used to treat mice experimentally infected with Aspergillus fumigatus, Cryptococcus neoformans, or Histoplasma capsulatum. In the models in which BRL and amphotericin B were compared, BRL was well tolerated but was less effective than a similar regimen of amphotericin B. However, the ability to give much larger doses of BRL than tolerated with amphotericin B suggest that this drug could be an alternative to amphotericin B.

Fluconazole treatment of Candida albicans infection in mice: does in vitro susceptibility predict in vivo response?

A series of fluconazole-susceptible and-fluconazole resistant Candida albicans fungal isolates were used to infect mice intravenously. Mice were treated with varying doses of fluconazole beginning one day after infection. For all of the 6 fluconazole-susceptible isolates, fluconazole was highly effective at <0.25 mg/kg of body weight twice daily. By contrast, fluconazole was less effective in at least 6 of 10 fluconazole-resistant isolates and was ineffective at > or = 40 mg/kg twice daily in 4 fluconazole-resistant isolates. Although the correlation is not precise, in vitro susceptibility testing of C. albicans can predict in vivo response to fluconazole.