RT Book, Section A1 Levinson, Warren A1 Chin-Hong, Peter A1 Joyce, Elizabeth A. A1 Nussbaum, Jesse A1 Schwartz, Brian SR Print(0) ID 1171925320 T1 Mycobacteria T2 Review of Medical Microbiology & Immunology: A Guide to Clinical Infectious Diseases, 16e YR 2020 FD 2020 PB McGraw Hill PP New York, NY SN 9781260116717 LK accessmedicine.mhmedical.com/content.aspx?aid=1171925320 RD 2024/11/03 AB Mycobacteria are aerobic, acid-fast bacilli (rods) (Figure 21–1). They are neither gram-positive nor gram-negative (i.e., they are stained poorly by the dyes used in Gram stain). They are virtually the only bacteria that are acid-fast. (One exception is Nocardia asteroides, the major cause of nocardiosis, which is also acid-fast.) The term acid-fast refers to an organism’s ability to retain the carbol fuchsin stain despite subsequent treatment with an ethanol–hydrochloric acid mixture. The high lipid content (approximately 60%) of their cell wall makes mycobacteria acid-fast.