BACKGROUND: C. rugosa is associated clinically with failure to AMB, and sometimes in vitro resistance to AMB. In an outbreak of C. rugosa in 6 patients, 5 succumbed including 4 treated with AMB. We conducted the following studies to search for useful therapeutic alternatives to AMB. METHODS: In vitro testing was done by NCCLS M27-A method for AMB, fluconazole (FLU), voriconazole (VORI), and posaconazole (POS). In vivo testing of antifungal activity was performed with 2 isolates in groups of 8-12 mice pretreated with cyclophosphamide at 200 mg/kg intraperitoneally (IP). Mice were infected intravenously with isolate 1 at 1-3x10 6 or with isolate 2 at 2.6x10 4 -5.6x10 6 CFU/mouse. Mice were treated from day 1-7 with water PO (controls), AMB at 0.3 or 1mg/kg IP, FLU at 0.5, 10 or 20 mg/kg BID PO, POS at 1 or 20 mg/kg PO, or VORI at 5 or 10mg/kg BID PO. All VORI treated mice were given grapefruit juice orally (0.2ml) beginning 3 days prior to commencing therapy and continuing through day 7. This is to impair intestinal cytochrome enzyme clearance of VORI, thereby increasing net absorption of VORI and extending the systemic half-life. Mice were observed 30 days for survival. In separate studies, to assess tissue burden of kidneys, mice were sacrificed on day 8. Counts were done by serial tenfold dilution. For survival studies, the logrank test of life tables was used. For tissue burden, the Mann Whitney test was used. P 0.5 mg/kg BID), and POS (> 1mg/kg) all significantly prolonged survival over controls. With isolate 2, AMB (1mg/kg), FLU (10mg/kg BID), VORI (10mg/kg BID), and POS (20mg/kg) significantly prolonged survival. With isolate 1, kidney counts were reduced significantly below controls for AMB (1mg/kg), FLU (20mg/kg BID), and POS (20 mg/kg). With isolate 2, kidney counts were reduced significantly below controls by AMB (1mg/kg), FLU (20mg/kg BID), and POS (20mg/kg). VORI did not reduce kidney counts with either isolate. CONCLUSIONS: Despite poor clinical response to AMB, in the present studies we found isolates were susceptible in vitro to AMB, and in vivo data suggested AMB did increase organ clearance and survival benefit over untreated controls. Both POS and FLU were effective in vitro and in vivo. However, while VORI did provide improved 30-day survival over control, increased tissue clearance was not demonstrated. This discrepancy may be caused by rapid clearance of VORI in mice. Clinical correlation in human studies is necessary, as VORI is cleared more slowly. These studies suggest FLU, POS or VORI may be useful alternatives to AMB in the setting of clinical failure of AMB therapy of C. rugosa infection.
Full conference title:
The 15 th Congress of the International Society for Human and Animal Mycology
- ISHAM 15th (2003)