Application of the novel fluorescent dye Beljian red to the differentiation of Giardia cysts

Beljian red (BR) is a novel long Stokes shift fluorescent dye that fluoresces orange when illuminated with UV or blue light. Due to its long Stokes shift, and the fact that it is excitable at 488 nm, BR has particular utility in multi-colour applications with short Stokes shift fluorophores such as fluorescein. Here we have demonstrated that BR can be used to discriminate Giardia cysts seeded into water samples from those naturally present in the sample. We show that the dye does not interfere with other staining methods such as DAPI, and is compatible with mAb-FITC staining in a multi-colour fluorescence technique. This should be useful in determining the specific recovery of protozoan parasites from environmental samples.