In-111 Pseudomonas aeruginosa: a simple method of labeling live bacteria with a gamma-emitting radioisotope

We describe a simple and reliable technique for labeling Pseudomonas aeruginosa with a readily available commercial preparation of indium-111 (111In) oxine. Labeling of a heavy bacterial suspension with 500 mu Ci of commercially prepared 111In-oxine resulted in a yield of 0.0004 mu Ci of cell-associated 111In per 10(6) colony-forming units (CFU). The label was 88% bacterially associated and did not effect viability of the organism. Radiolabeling a gram-negative organism with 111In-oxine provides a non-toxic, stable gamma-emitting bacterial tracer.