Löwenstein–Jensen medium

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Löwenstein–Jensen medium
Löwenstein-Jensen agar
Löwenstein-Jensen medium used for growing M. tuberculosis in a McCartney bottle.
Acronym LJ medium
Uses Culturing
Related items Petri dish
Growth medium

The Löwenstein–Jensen medium, more commonly known as LJ medium, is a growth medium[1] specially used for culture of Mycobacterium, notably Mycobacterium tuberculosis.

When grown on LJ medium, M. tuberculosis appears as brown, granular colonies (sometimes called "buff, rough and tough"). The media must be incubated for a significant length of time, usually four weeks, due to the slow doubling time of M. tuberculosis (15–20 hours) compared with other bacteria.

Composition[edit]

The usual composition[2] as applicable to Mycobacterium tuberculosis is:

The original formulation included starch, which was later found to be unnecessary and hence omitted.

Low levels of penicillin and nalidixic acid are also present in LJ medium to inhibit growth of gram positive and gram negative bacteria, in order to limit growth to Mycobacteria species only. Presence of malachite green in the medium inhibits most other bacteria. It is disinfected and solidified by a process of inspissation. Presence of glycerol enhances the growth of Mycobacterium tuberculosis.

If the slopes are made on test tubes they must be stored in cold and used within a month.

For cultivation of M.bovis, glycerol is omitted and sodium pyruvate is added.

The medium appears green, opaque and opalescent.

Uses[edit]

  • For diagnosis of Mycobacterial infections
    Distinctive clusters of colorless Mycobacterium tuberculosis
  • For testing antibiotic susceptibility of isolates
  • For differentiating different species of mycobacterium (by colony morphology, growth rate, biochemical characteristics and microscopy)
Mycobacterium tuberculosis Mycobacterium Bovis
Eugonic, rough tough and buff Dysgonic
Aerobic Microaerophillic
Glycerol enhancement + Glycerol enhancement -
Pyruvate enhancement + Pyruvate enhancement -
Niacin production + Niacin production -

Alternatives[edit]

Alternative culture media[edit]

While the LJ medium is the most popular means of culturing Mycobacteria, as recommended by the International Union against Tuberculosis (IUAT), several alternative media have been investigated.[3]

Solid media[edit]

Liquid media[edit]

Rapid detection techniques[edit]

The chief limitation of culture based techniques is the time it takes to culture positivity, which can be several months. Several new molecular technologies have emerged in recent years to secure more speedy confirmation of diagnosis.

See also[edit]

References[edit]