Objectives: The aim of the present study was to evaluate the effects of delay the antifungal therapy on the outcome of invasive aspergillosis (IA) due to A. fumigatus in experimental models of infections.
Methods: A clinical isolate of A. fumigatus susceptible to both amphotericin B (AMB, median MIC 0.5 μg/ml) and micafungin (MICA, median MEC 0.03 μg/ml) was used in all experiments. Two models of infections were investigated in CD1 immunosuppressed female mice:
disseminated infection (DI) performed by given the conidia intravenously and pulmonary infection (PI) by given the conidia intranasally. 24 h (early therapy, ET) and 48 h (delayed therapy, DT) postinfection, the mice were given placebo, MICA, liposomal-AMB (L-AMB), and MICA plus L-AMB (Combo). Each drug was utilized at low (3 mg/kg/day) and high (10 mg/kg/day) doses. Therapy was given for three consecutive days. Drug efficacy was assessed either by survival analysis (15 days of observation) or tissue burden experiments (kidney and lung in DI and PI models, respectively). In tissue burden the mice were euthanized 24 h after the last dose of the drug and tissue CFUs were determined. Histology studies were also performed. Survivals were plotted as Kaplan-Meier curves and analyzed by log rank (due to multiple comparison, a P < 0.008 was considered statistically significant). CFUs/organ/mouse were analyzed by one-way Anova followed by the Tukey's test corrected for multiple comparison (a P <0.05 was considered statistically significant).
Results: In ET of DI model either L-AMBI (P = 0.0024) or MICA (P = 0.0031) given at 3 mg were effective against the control at prolonging the survival. Combo was more effective than control (P <0.0001), more effective than L-AMBI (P = 0.0005) but not more effective than MICA alone (P = 0.02). In DT, the only regimen which prolonged the survival was Combo (P = 0.005). When drug doses, singly and in combination, were increased at 10 mg, all regimens were effective at prolonging the survival following ET (P <0.0001). In DT experiments,
only MICA (P = 0.001) and Combo (P = 0.0026) were effective. PI was conducted with drugs given at 3 mg. In both ET and DT experiments only Combo was more effective than control at prolonging the survival (P = 0.007 in ET, P = 0.004 in DT). In ET of tissue burden
experiments each single regimen given at 3 mg was effective in DI model, while only L-AMB and Combo were effective in PI model. Conversely, in DT no regimen was effective.
Conclusion: The delay onset of therapy is deleterious in experimental models of IA either in terms of survival than in terms of fungal burden. A combination approach seems to be a good therapeutic option when therapy is started late.