The Modified Ziehl-Neelsen stain (mZN stain) is a type of differential bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. Acid fast organisms are those which are capable of retaining the primary stain when treated with an acid (fast=holding capacity). Members of the Actinomycetes, genus Nocardia (N. brasiliensis and N. asteroides are opportunistic pathogens) are partially acid-fast. Oocysts of coccidian parasites, such as Cryptosporidium and Isospora, are also acid-fast. Hence they can also be detected and identified through mZN staining procedure.