acid-fast
UK[ˈæsɪd fɑːst]US[ˈæsɪd fæst]
adj
(of bacteria) not easily decolorized by acids after staining, especially denoting the tubercle bacillus and some other bacteria.
Morpheme Breakdown
acid
fast
acid
fast
Etymology
The term "acid-fast" is a modern scientific compound, directly combining two English words to describe a specific physical property. The first element, "acid," retains its Latin-derived meaning of a corrosive chemical substance. The second element, "fast," draws from its Old English sense of being firm, fixed, or steadfast. Literally, the compound means "firm against acid," a logical description for microorganisms that resist decolorization by strong acids during laboratory staining procedures, a key diagnostic feature discovered in the late 19th century.
Analysis
Structure: acid + fast
- acid: From Latin acidus (sour, sharp), functioning as a noun/adjective root denoting a chemical substance.
- fast: From Old English fæst (firm, fixed, secure), functioning as an adjective/adverb meaning resistant or stable.
Examples
The Ziehl-Neelsen stain is used to identify acid-fast bacilli like Mycobacterium tuberculosis.
Acid-fast staining is a crucial technique in clinical microbiology for diagnosing certain bacterial infections.
Due to their unique cell wall composition, these bacteria are acid-fast.