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Mycobacterium tuberculosis (M. tb), also known as Koch's bacillus, is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. [ 1 ] [ 2 ] First discovered in 1882 by Robert Koch , M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid .
The abbreviation TB is short for tubercle bacillus. Consumption was the most common nineteenth century English word for the disease, and was also in use well into the twentieth century. The Latin root con meaning 'completely' is linked to sumere meaning 'to take up from under'. [204]
Tuberculin is a glycerol extract of the tubercle bacillus. Purified protein derivative (PPD) tuberculin is a precipitate of species-nonspecific molecules obtained from filtrates of sterilized, concentrated cultures. The tuberculin reaction was first described by Robert Koch in 1890.
Tubercle bacilli, either free or within phagocytes, drain to the regional nodes, which also often caseate. This combination of parenchymal lung lesion and nodal involvement is referred to as the Ghon complex. During the first few weeks, there is also lymphatic and hematogenous dissemination to other parts of the body.
The exact mechanism of tuberculoma development has not been determined, although multiple theories have been proposed. It is possible that, following an initial tuberculosis infection resulting in bacteremia, a foci of granulomatous inflammation may coalesce into a caseous tuberculoma. [20]
Short, relatively plump bacilli (rods) in tissue smears, large slender beaded rods in culture. They have no flagella or fimbria, and no capsule. [citation needed] Mycobacterium tuberculosis group bacteria are 1.0-4.0 μm long by 0.2-0.3 μm wide in tissues. In culture, they may appear as cocci, or as bacilli up to 6-8 μm long. [citation needed]
Nodules and fibrotic scars may contain slowly multiplying tubercle bacilli with the potential for future progression to active tuberculosis. [1] Persons with these findings, if they have a positive tuberculin skin test reaction, should be considered high-priority candidates for treatment of latent infection regardless of age.
Heinrich Hermann Robert Koch (/ k ɒ x / KOKH; [1] [2] German: [ˈʁoːbɛʁt ˈkɔx] ⓘ; 11 December 1843 – 27 May 1910) was a German physician and microbiologist.As the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera and anthrax, he is regarded as one of the main founders of modern bacteriology.