Löwenstein–Jensen medium, more commonly known as LJ medium, is a

growth medium A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Differen ...

specially used for culture of ''

Mycobacterium ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') and ...

'' species, notably ''

Mycobacterium tuberculosis ''Mycobacterium tuberculosis'' (M. tb) is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, ''M. tuberculosis'' has an unusual, waxy coating on its c ...

''. When grown on LJ medium, ''M. tuberculosis'' appears as brown, granular colonies (sometimes called "buff, rough and tough"). The medium 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. The medium is named after the Austrian pathologist Ernst Löwenstein (1878–1950) and the Danish medical doctor Kai Adolf Jensen (16.7.1894-2.5.1971).

Composition

The usual composition as applicable to ''M. tuberculosis'' is: * Malachite green * Glycerol * Asparagine * Potato starch * Coagulated eggs * Mineral salt solution **

Potassium dihydrogen phosphate Monopotassium phosphate (MKP) (also, potassium dihydrogenphosphate, KDP, or monobasic potassium phosphate) is the inorganic compound with the formula KH2PO4. Together with dipotassium phosphate (K2HPO4.(H2O)x) it is often used as a fertilizer, ...

** Magnesium sulfate ** Sodium citrate The original formulation included starch, which was later found to be unnecessary, so omitted. Low levels of

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...

and nalidixic acid are also present in LJ medium to inhibit growth of Gram-positive and Gram-negative bacteria, to limit growth to ''Mycobacterium'' species only. Presence of malachite green in the medium inhibits most other bacteria. It is disinfected and solidified by a process of

inspissation Inspissation is the process of thickening by dehydration. Intentional use Inspissation is the process used when heating high-protein containing media; for example to enable recovery of bacteria for testing. Once inspissation has occurred, any stain ...

. Presence of glycerol enhances the growth of ''M. 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

* For diagnosis of mycobacterial infections * For testing antibiotic susceptibility of isolates * For differentiating different species of ''Mycobacterium'' (by colony morphology, growth rate, biochemical characteristics, and microscopy)

Alternatives

Alternative culture media

While LJ medium is the most popular means of culturing mycobacteria, as recommended by the International Union against Tuberculosis, several alternative media have been investigated.

Solid media

* Egg-based – Petragnani medium and Dorset medium * Middlebrook 7H10 agar *

Middlebrook 7H11 agar Middlebrook 7H11 agar is identical to Middlebrook 7H10 agar, with an addition of pancreatic digest of casein to facilitate the growth of fastidious cultures of '' M. tuberculosis''. Mycobactin J may also be added to Middlebrook 7H11 agar to allow ...

* Blood-based – Tarshis medium * Serum-based – Loeffler medium * Potato-based – Pawlowsky medium

Liquid media

* Dubos' medium *

Middlebrook 7H9 broth Middlebrook 7H9 broth is a liquid growth medium specially used for culture of'' Mycobacterium'' species, notably '' Mycobacterium tuberculosis''. Composition * Ammonium sulfate * L-Glutamic acid * Sodium citrate * Pyridoxine * Biotin * Disodium ph ...

* Proskauer and Beck's medium * Sula's medium * Sauton's medium

Rapid detection techniques

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. * Polymerase chain reaction * GeneXpert MTB/RIF * Loop-mediated isothermal amplification

References

{{DEFAULTSORT:Lowenstein-Jensen medium Microbiological media