Mycobacterium tusciae is a slow-growing, scotochromogenic mycobacterium

Mycobacterium

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy...

 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

Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

: 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
  Microscopic
  The microscopic scale is the scale of size or length used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...
  
   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, (asbestos) can also be a cause.

Pathophysiology

• The lymph nodes irritation causes a response by the dust cell
  Dust cell
  An alveolar macrophage is a type of macrophage found in the pulmonary alveolus, near the pneumocytes, but separated from the wall....
  
  s/alveolar macrophages, which cause enzymes, complement proteins, and regulatory factors such as interleukin-1 to get produced.
• The macrophages also carry receptors for lymphokines, and lymphoines 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
  Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
  
   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 macrophages 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 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 macrophages 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
  Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
  
  .

Differential characteristics

• Closely related to Mycobacterium aichiense
  Mycobacterium aichiense
  Mycobacterium aichiense is a yellow-orange scotochromogenic, rapidly growing mycobacterium first isolated from soil and human sputum in Japan. It has not been formally associated with disease in humans.-Description:Microscopy...
  
   and Mycobacterium farcinogenes
  Mycobacterium farcinogenes
  Mycobacterium farcinogenes is a species of Mycobacterium.Although slow-growing, it is similar to fast-growing species, and is usually classified with them.-Description:...
  
  , rapidly-growing mycobacteria, 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.