Methylene Blue Loeffler reagent is used for staining acidoresistant bacteria according to Ziehl-Neelsen, utilizing the dye's property to stain almost all the bacterial cell's elements in a mildly alkaline medium (Methylene Blue Loeffler reagent has pH value of 8-8.5).

Application

The Löffler's alkaline methylene blue staining method is a simple staining technique that can be used to differentiate bacterial, viral, and fungal infections. ... Specimens collected from patients by swabbing are smeared onto microscope slides and the methylene blue solution is dropped on the slide.