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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 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).
This time period can, therefore, be referred to as the doubling time. Some species other than E. coli may have faster or slower doubling times: some strains of Mycobacterium tuberculosis may have doubling times of nearly 100 hours. [12]
Mycobacterium orygis is an obligate aerobe, and a facultative intracellular pathogen. It has a doubling time of 15–20 hours within cells, and longer when outside cells. Mycobacterium orygis uses the host's cells internal fatty acids for both a carbon source and an energy source.
Middlebrook 7H9 broth supports the growth of mycobacterial species when supplemented with nutrients such as glycerol, oleic acid, albumin, and dextrose, except for Mycobacterium bovis, which is inhibited by glycerol. Cultures should be read within 5–7 days after inoculation and once a week thereafter for up to 8 weeks.
This instrument is produced by Becton Dickinson (BD). It is specially designed to accommodate Mycobacteria Growth Indicator Tube (MGIT) and incubate them at 37 °C. The instrument scans the MGIT every 60 minutes for increased fluorescence.
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H37Rv has continued to be the strain of tuberculosis most used in laboratories, and was the first to have its complete genome published in 1998. [5] It is unclear how much H37Rv may have evolved in more than 100 years under artificial conditions in laboratories from strains in the wild, but its genome is similar to a strain isolated from a 19th ...