infectious diseases
Microscopy
Fluorescent stains
Fluorescent stains allow detection at lower concentrations (< 1×104cells/mL). Examples are Acridine orange (bacteria and fungi) Auramine-rhodamine and auramine O (mycobacteria) Calcofluor white (fungi, especially dermatophytes) Coupling a fluorescent dye to an antibody directed at a pathogen (direct or indirect immunofluorescence) should theoretically increase sensitivity and specificity. However, these tests are difficult to read and interpret, and few (eg,PneumocystisandLegionelladirect fluorescent antibody tests) are commercially available and commonly used. 