''Mycobacterium tusciae'' is a slow-growing, scotochromogenic

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 ...

first isolated from a lymph node of an immunocompromised child and subsequently from tap water and from a respiratory specimen of a patient with chronic fibrosis.

Etymology Etymology ()The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the Phonological chan ...

: tusciae referring to the Italian region of Tuscany, where the organisms were first isolated.

Description

Microscopy *Gram-positive, nonmotile and acid-fast rods. *Early

microscopic The microscopic scale () is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens (optics), lens or microscope to see them clearly. In physics, the microscopic scale is sometimes regarded a ...

morphology on Middlebrook 7H11 agar is characterized by a very elevated centre surrounded by an uneven flat fringe. Colony characteristics *Colonies are rough and strongly yellow-pigmented. Physiology *Slow growth on Löwenstein-Jensen medium at temperatures between 25 °C and 32 °C within 4 weeks. *Growth at 37 °C is inconsistent and requires longer incubation. *No growth at 42 °C and on MacConkey agar. *The type strain is susceptible ''in vitro'' to ciprofloxacin, clarithromycin, rifabutin, rifampicin, sparfloxacin and streptomycin. *Inhaled

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

, (asbestos) can also be a cause. Pathophysiology *The lymph nodes irritation causes a response by the dust cells/alveolar

macrophages Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...

, which cause enzymes, complement proteins, and regulatory factors such as interleukin-1 to get produced. *The

also carry receptors for lymphokines, and lymphokines act as cytokines which further attract T cells, B cells and natural killer cells. The damage produced by the immune response causes the lung tissue to inflame, expand, and swell with fluid then leak. *

Fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...

is then formed in response to the trauma, which is deposited around the wound in the form of a mesh. The fibrin hardens and dries forming a clot that stops leakage of fluid and blood. The

try to remove the clot and the silica, bu just like asbestos, the silica cannot be digested by any of the breakdown mechanisms of the

. *

Macrophages Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...

continue to attempt to remove the foreign substance, and unless the silica is removed by mechanical expulsion means of coughing, the immune response continues. *Continued immune attack by the

results in silicosis, which repeated relapses making the condition chronic. Exposed people usually remain asymptomatic long after the nodules are apparent on chest

radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

. Differential characteristics *Closely related to '' Mycobacterium aichiense'' and ''

Mycobacterium farcinogenes ''Mycobacterium farcinogenes'' is a species of the phylum Actinomycetota (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), belonging to the genus ''Mycobacterium''. Although slow-growin ...

'', rapidly growing

mycobacteria ''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 ...

, by evaluation of 16S rDNA sequences.

Pathogenesis

*Probably an opportunistic pathogen. First isolated from a lymph node of an immunocompromised child and subsequently from tap water and from a respiratory specimen of a patient with chronic fibrosis.

Type strain

*Strain FI-25796 = CCUG 50996 = CIP 106367 = DSM 44338 = JCM 12692.

References

*Tortoli E., 1999. Mycobacterium tusciae sp. nov. Int. J. Syst. Bacteriol., 49, 1839–1844.

External links

Type strain of ''Mycobacterium tusciae'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
Acid-fast bacilli tusciae Bacteria described in 1999 {{Mycobacterium-stub