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ac·id-fast ba·cil·lus(AFB) (asid-fast bă-silŭs)
A type of bacterium that reacts in a given way when treated with an acid bath.
acid-fast bacillusAbbreviation: AFB
A bacillus not readily decolorized by acids or other means when stained. Mycobacterium tuberculosis is an acid-fast bacillus.
See also: bacillus