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Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining
Staining (biology)

Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image.In biochemistry it involves adding a class-specific dye to a substrate to qualify or quantify the presence of a specific compound....
 procedures.

Acid-fast organisms are difficult to characterize using standard microbiological techniques (e.g. Gram staining), though they can be stained using concentrated dyes, particularly when the staining process is combined with heat. Once stained, these organisms resist the dilute acid and/or ethanol-based de-colorization procedures common in many staining protocols—hence the name acid-fast.

The high mycolic acid
Mycolic acid

Mycolic acids are long fatty acids found in the cell walls of the Mycobacterium taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis....
 content of certain bacterial cell wall
Cell wall

A cell wall is a tough, flexible and sometimes fairly rigid layer that surrounds some types of cell . It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism....
s, like those of Mycobacteria, is responsible for the staining pattern of poor absorption followed by high retention.






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Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining
Staining (biology)

Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image.In biochemistry it involves adding a class-specific dye to a substrate to qualify or quantify the presence of a specific compound....
 procedures.

Acid-fast organisms are difficult to characterize using standard microbiological techniques (e.g. Gram staining), though they can be stained using concentrated dyes, particularly when the staining process is combined with heat. Once stained, these organisms resist the dilute acid and/or ethanol-based de-colorization procedures common in many staining protocols—hence the name acid-fast.

The high mycolic acid
Mycolic acid

Mycolic acids are long fatty acids found in the cell walls of the Mycobacterium taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis....
 content of certain bacterial cell wall
Cell wall

A cell wall is a tough, flexible and sometimes fairly rigid layer that surrounds some types of cell . It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism....
s, like those of Mycobacteria, is responsible for the staining pattern of poor absorption followed by high retention. The most common staining technique used to identify acid-fast bacteria is the Ziehl-Neelsen stain
Ziehl-Neelsen stain

The Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors; Franz Ziehl , a bacteriologist and Friedrich Neelsen , a pathologist....
, in which the acid fast bacilli are stained bright red and stand out clearly against a blue background. Another method is the Kinyoun method, in which the bacteria are stained bright red and stand out clearly against a green background. Acid-fast bacteria can also be visualized by fluorescence microscopy
Microscopy

Microscopy is the technical field of using microscopes to view samples or objects. There are three well-known branches of microscopy, optical microscopy, electron microscopy and scanning probe microscopy....
 using specific fluorescent dyes (auramine-rhodamine stain
Auramine-rhodamine stain

The auramine-rhodamine stain , also known as the Truant auramine-rhodamine stain, is a histology technique used to visualizee Acid-fast using microscopy#Fluorescence microscopy, notably species in the Mycobacterium genus....
, for example). Some bacteria may also be partially acid-fast.

Notable Acid fast structures


Very few structures are acid fast, this makes staining for acid-fastness particularly useful in diagnosis.

  • All Mycobacteria - M.tuberculosis, M.Leprae, M.smegmatis and atypical Mycobacterium
  • Nocardia
    Nocardia

    Nocardia is a genus of weakly-staining Gram-positive, catalase, rod-shaped bacteria. It has total 85 species. Some species are non pathogenic; some species are pathogenic ....
  • Head of sperm
    Sperm

    The term sperm is derived from the Greek word sperma and refers to the male reproductive Cell . In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell....
  • Bacterial spores
  • Cryptosporidium parvum
    Cryptosporidium parvum

    'Cryptosporidium parvum' is one of several species that cause cryptosporidiosis, a parasitic disease of the mammalian intestine .Primary symptoms of C....
    , Isospora
    Isospora

    Isospora is a genus of internal parasites classified under Coccidia.It is responsible for the condition isosporiasis.External links...
     and Cyclospora cysts


Online protocol examples

  • protocol (PDF
    Portable Document Format

    Portable Document Format is a file format created by Adobe Systems in 1993 for document exchange. PDF is used for representing two-dimensional documents in a manner independent of the application software, hardware, and operating system....
     format).
  • Alternate for staining AFB.