A PCR using primers aimed at the multicopy gene coding for the small subunit rRNA and resulting in the synthesis of a 180-bp fragment was evaluated for its use in diagnosing invasive candidiasis in comparison with blood culture. With the use of a C. albicans-specific probe, ؎10 to 15 C. albicans cells are detected in 100 l of whole blood by Southern analysis. A DNase pretreatment was critical in the purification process of yeast DNA from whole blood. Omission of the DNase pretreatment decreased assay sensitivity 10-fold. PCR analysis of blood specimens collected from mice with invasive candidiasis is more sensitive than blood culture (100 versus 67%, respectively) at 72 h after intravenous (i.v.) inoculation with C. albicans. Furthermore, the intensity of the hybridization signals increased with the progression of infection. In contrast, multiple blood samples from gastrointestinally colonized mice were all negative by PCR, indicating that the PCR assay is also specific and may, therefore, make a positive contribution to the detection and follow-up of invasive candidiasis.
The biodistribution of liposomal amphotericin B (L-AmB; AmBisome) and amphotericin B-desoxycholate were compared after a single injection of drug in uninfected immunocompetent mice and in leucopenic mice 6 h after inoculation with Candida albicans. Amphotericin B-desoxycholate was administered at the maximum tolerated dose (MTD) of 0.3 mg/kg whereas L-AmB was given at either 0.3 mg/kg or the MTD of 7 mg/kg. Amphotericin B (AmB) concentrations in the blood, liver, spleen, lungs and kidneys were determined by HPLC analysis at various intervals during the 48 h after administration. The biodistribution of both preparations of AmB followed similar patterns in both uninfected immunocompetent mice as well as those that were leucopenic and infected with C. albicans. Administration of L-AmB resulted in increased concentrations of drug in the blood, liver, and spleen but decreased concentrations in the kidney and lung. Hepatosplenic uptake of L-AmB was highly dose dependent with 7 mg/kg resulting in a relatively prolonged blood circulation. Blood and tissues retained high AmB concentrations after administration of L-AmB at the MTD. By using radiolabelled L-AmB, it was found that the high AmB concentrations in blood represented liposome-associated AmB and that during circulation in blood slow release of AmB occurred.
The nebulization of amphotericin B desoxycholate (AMB-DOC), liposomal amphotericin B (L-AMB), amphotericin B lipid complex (ABLC) and amphotericin B colloidal dispersion (ABCD) has been investigated. Particle sizes of generated aerosol droplets were measured. Pulmonary amphotericin B deposition and amphotericin B concentration in blood directly after nebulization and at six weeks after nebulization was measured in healthy rats. The efficacy of nebulized amphotericin B formulations was evaluated in persistently granulocytopenic rats with invasive pulmonary aspergillosis. Treatment was given either after or before fungal inoculation. The endpoint was survival of animals. Aerosol particle sizes, expressed as the values for the mass median diameter were 1.38, 2.43, 0.90 and 2.29 microm for AMB-DOC, L-AMB, ABLC and ABCD, respectively. Amphotericin B concentrations in the lungs directly after nebulization exceeded the minimum inhibitory concentration of Aspergillus fumigatus and amphotericin B was still detected in lungs of rats at six weeks after nebulization. Treatment, started at 16 h after fungal inoculation, resulted in a significantly prolonged survival as compared with sham-treated rats for all four formulations. Prophylactic treatment at one week before fungal inoculation resulted in a significantly prolonged survival for all four formulations. Aerosol treatment given at two weeks before inoculation was effective only for AMB-DOC and L-AMB, whereas treatment given at six weeks resulted in a significantly prolonged survival for L-AMB only. All commercially available amphotericin B preparations could be nebulized efficiently and may be of value in the prophylactic treatment of invasive pulmonary aspergillosis.
The effects of treatment with aerosolized amphotericin B desoxycholate and aerosolized liposomal amphotericin B were evaluated in severely immunosuppressed rats with invasive pulmonary aspergillosis. Aerosol treatment with amphotericin B desoxycholate consisted of a single dose (60 min) with amphotericin B concentrations in the nebulizer reservoir of 1, 2 and 4 mg/mL, respectively. For liposomal amphotericin B, aerosol treatment consisted of single, double or quadruple doses with a nebulizer reservoir concentration of 4 mg/mL of amphotericin B. Treatment, started at 30 h after inoculation, with aerosolized amphotericin B desoxycholate (nebulizer reservoir concentration 2 mg/mL) significantly prolonged survival of rats as compared with placebo-treated rats, whereas treatment with aerosolized amphotericin B desoxycholate with nebulizer reservoir concentration of 1 or 4 mg/mL did not have a significant effect on survival. Treatment with aerosolized liposomal amphotericin B signifcantly prolonged survival with all treatment regimens when compared with placebo-treated animals. Aerosol treatment did not prevent dissemination of the infection. The effects of amphotericin B desoxycholate and liposomal amphotericin B on pulmonary surfactant function were also evaluated in vitro. Amphotericin B desoxycholate inhibited surfactant function in a dose-dependent fashion. Liposomal amphotericin B had no detrimental effect on surface activity of surfactant. These results indicate that aerosol administration of amphotericin B, especially the liposomal formulation, could be an additional approach to optimizing treatment of invasive pulmonary aspergillosis.
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