Background: Accurate quantification of fungal burden is essential in measuring the efficacy of novel antifungal drugs against AF. Correlations between Taqman (qPCR) assay and CFU determination were evaluated to assess progressive infection in untreated mice as well as CAS efficacy. Methods: Neutropenic CD-1 mice were infected intracranially with 5.8 x 106 conidia of AF. Groups of 10 were treated once daily with 1, 5, or 10 mg/kg of CAS (i.p.) or 3 mg/kg of amphotericin B (AmB) (i.p.) for 4 d starting 1 d postinfection. To assess progressive infection in brains and kidneys, untreated controls (n = 10-12 each day) were euthanized on d 1, 3, and 5; treated animals were euthanized on d 5. Fungal burdens in each sample were determined by plating organ homogenates for CFU and by qPCR. Results: qPCR showed higher burdens than CFU in all comparisons. For untreated animals, qPCR showed increased burdens in brain from d 1 to 3 (P = 0.015), while CFU showed a decrease from d 1 to 3 and 5 (P £ 0.023). qPCR showed increased burdens in kidneys from d 1 to 3 and 5 (P £ 0.0001), while no significant changes were seen with CFU. Neither method showed drug efficacy in the brain. Both methods showed AmB efficacy in the kidneys (P £ 0.012), and qPCR demonstrated CAS efficacy at all doses (P £ 0.027), while CFU did not. Spearman correlations of qPCR and CFU for individual mice showed a significant correlation for untreated groups, except for d 3 brains and d 5 kidneys; assay results correlated well for kidneys (P £ 0.03) but not for brains in treated mice. For both organs, regression analyses of qPCR and CFU groups indicated that slopes were different for progressive infection in untreated animals (P £ 0.005) but equal for CAS dose-response efficacy. Conclusions: Although qPCR better reflects temporal progression of untreated infection, either qPCR or CFU appear useful for determining AF burdens at a single time at the conclusion of a drug efficacy study.
Full conference title:
43rd Interscience Conference on Antimicrobial Agents
- ICAAC 43rd