111In-DTPA-Biotin uptake by Staphylococcus aureus

The potential of indium-111 labelled diethylenetriaminepentaacetic acid αω-bis(biocytinamide) (111In-DTPA-Biotin) as a specific tracer in nuclear medicine imaging of vertebral osteomyelitis has been shown in a large series of consecutive patients. Biocytin is known to serve as a biotin source for a number of different microorganisms and quantitative studies on staphylococci indicated that on a molar basis biocytin seemed to have an activity equal to that of biotin. In this study, we evaluated the possibility of an illicit transport of 111In-DTPA-Biotin in cultures of Staphylococcus aureus on continued incubation for 24 h. Radiolabelled biocytin was prepared as described earlier and the stability and radiochemical purity was assessed in vitro for 24 h after labelling. Our data seem to demonstrate a passive transport of 111In-DTPA-Biotin into the cells of the microrganisms.