Question: what group of organisms are considered acid fast

title: Acid-fastness
text: All Mycobacteria - M. tuberculosis , M. leprae , M. smegmatis and atypical Mycobacterium Actinomycetes ( especially some aerobic ones ) with Mycolic acid in their cell wall ( note Streptomyces do NOT have ) ; not to be confused with Actinomyces , which is a non-acid - fast genera of Actinomycetes Nocardia Rhodococcus Gordonia ( Actinomycete ) Tsukamurella Dietzia Head of sperm Bacterial spores , see Endospore Legionella micdadei Certain cellular inclusions e.g. Cytoplasmic inclusion bodies seen in Neurons in layer 5 of cerebral cortex neuronal ceroid lipofuscinosis ( Batten disease ) . Nuclear inclusion bodies seen in Lead poisoning Bismuth poisoning . Oocysts of some coccidian parasites in faecal matter , such as : Cryptosporidium parvum , Isospora belli Cyclospora cayetanensis . A few other parasites : Sarcocystis Taenia saginata eggs stain well but Taenia solium eggs do n't ( Can be used to distinguish ) Hydatid cysts , especially their `` hooklets '' stain irregularly with ZN stain but emanate bright red fluorescence under green light , and can aid detection in moderately heavy backgrounds or with scarce hooklets . Fungal yeast forms are inconsistently stained with Acid - fast stain which is considered a narrow spectrum stain for fungi . In a study on acid - fastness of fungi , 60 % of blastomyces and 47 % of histoplasma showed positive cytoplasmic staining of the yeast - like cells , and Cryptococcus or candida did not stain , and very rare staining was seen in Coccidioides endospores .