Effect of Treatment with Caspofungin on the Diagnosis of Fungal Infections by Gamma Scintigraphy

The aim of this work was to assess the influence of treatment with U-Caspofungin, on the quality of diagnostic scintigraphic images of induced lesions in nude mice undergoing both bacterial and fungal infections and to determine the level of specificity of 99mTc-tricarbonyl-Caspofungin to discriminate between fungal or bacterial infections. In vitro studies on the behaviour of the 99mTc-tricarbonyl-Caspofungin complex binding percentage at different yeast concentrations of Candida albicans or Staphyolococcus aureus were determined. The incubation was performed with and without U-Caspofungin. In vivo evaluation was performed of 6 groups of athymic mice: sham, inflammation (LPS), fungal infection with Candida albicans (CA) and bacterial infection with Staphylocuccus aureus (SA). In vitro studies showed that the uptake of the complex by both yeasts and bacteria, depends on the concentration of colony forming units (cfu), and that this uptake is favoured by the presence of UCaspofungin that increases the membrane permeability to the 99mTc-tricarbonyl-Caspofungin complex. In vivo evaluation showed low uptake in sterile inflammation model and moderate to high uptake in infections models both treated or not with U-Caspofungin. The results of biodistributions were compatible with scintigraphic images. Conclusion: The uptake of the complex depends on the load of microorganisms, but it presents high sensibility, even at low concentrations of the infecting agent. The treatment with U-Caspofungin has no influence on the quality of the scintigraphic images used for diagnosis and localization of infection foci.