| Mycobacterium tuberculosis | ||||||||||||||
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 M. tuberculosis bacterial colonies | ||||||||||||||
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| Mycobacterium tuberculosis Zopf 1883 |
Mycobacterium tuberculosis is the bacterium that causes most cases of tuberculosis. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common [1]
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History
M. tuberculosis, then known as the "tubercle bacillus," was first described on March 24, 1882 by Robert Koch, who subsequently received the Nobel Prize in physiology or medicine for this discovery in 1905; the bacterium is also known as Koch's bacillus. In anatomy a tubercle is a round Nodule, small Eminence, or Warty outgrowth found on Bones skin or within the lungs in Tuberculosis Events 1401 - Mongol emperor Timur sacks Damascus. 1603 - James VI of Scotland Year 1882 ( MDCCCLXXXII) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common Heinrich Hermann Robert Koch ( December 11 1843 – May 27 1910) was a German Physician. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. Heinrich Hermann Robert Koch ( December 11 1843 – May 27 1910) was a German Physician. The M. tuberculosis genome was sequenced in 1998[2][3]
Physiology
M. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby For the sense of "sequencing" used in Electronic music, see the Music sequencer article Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) tuberculosis is an obligate aerobe (weakly Gram-positive mycobacterium, hence Ziehl-Neelsen staining (Acid-fast staining) is used). An aerobic organism or aerobe is an Organism that has an Oxygen based Metabolism. Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. Mycobacterium is a Genus of Actinobacteria, given its own family the Mycobacteriaceae The Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors Franz Ziehl (1859 to 1926 a bacteriologist and Friedrich While mycobacteria do not seem to fit the Gram-positive category from an empirical standpoint (i. e. , they do not retain the crystal violet stain), they are classified as acid-fast Gram-positive bacteria due to their lack of an outer cell membrane. Methyl violet is the name given to a group of similar Chemicals used as PH indicators and Dyes Methyl violets are mixtures of tetramethyl pentamethyl and Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures The outer membrane refers to the outside membranes of Gram-negative bacteria, the Chloroplast, or the Mitochondria. [1]
M. tuberculosis divides every 15 to 20 hours, which is extremely slow compared to other bacteria, which tend to have division times measured in minutes (for example, E. coli can divide roughly every 20 minutes). It is a small bacillus that can withstand weak disinfectants and can survive in a dry state for weeks. This page is about the bacterial genus For the class see Bacilli. Disinfectants are Antimicrobial agents that are applied to non-living objects to destroy Microorganisms, the process of which is known as disinfection. Its unusual cell wall, rich in lipids (e. g. , mycolic acid), is likely responsible for this resistance and is a key virulence factor. [4]
When in the lungs, M. tuberculosis is taken up by alveolar macrophages, but they are unable to digest the bacterium. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Its cell wall prevents the fusion of the phagosome with a lysosome. In cell biology a phagosome is a Vacuole formed around a particle absorbed by Phagocytosis. Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases. Specifically, M. tuberculosis blocks the bridging molecule, early endosomal autoantigen 1 (EEA1); however, this blockade does not prevent fusion of vesicles filled with nutrients. Consequently, the bacteria multiply unchecked within the macrophage. The bacteria also carried the UreC gene, which prevents acidification of the phagosome[5]. The bacteria also evade macrophage killing by neutralizing reactive nitrogen intermediates.
Genome
The genome of the H37Rv strain was published in 1998. [6] It's size is 4 million base pairs, with 3959 genes. 40% of these genes have had their function characterised, with possible function postulated for another 44%. Within the genome are also 6 pseudogenes.
The geneome contains 250 genes involved in fatty acid metabolism, with 39 of these involved in the polyketide metabolism generating the waxy coat. Such large numbers of conserved genes shows the evolutionary importance of the waxy coat to pathogen survival.
10% of the coding capacity is taken up by 2 clustered gene families that encode acidic glycine rich proteins. These proteins have a conserved N-terminal motif, deletion of which impairs growth in macrophages and granulomas. [7]
Diagnosis
Sputum is taken in 3 successive mornings as the number of organisms could be low, and the specimen is treated with 3% KOH or NaOH for liquefaction and decontamination. Sputum is matter that is Expectorated from the respiratory tract such as Mucus or Phlegm, mixed with Saliva, which can then be spat Potassium hydroxide is the Inorganic compound with the formula K[[hydroxide OH]] Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature Gram stain should never be performed, as the organism is an "acid-fast bacillus" (AFB), meaning that it retains certain stains after being treated with acidic solution. Gram staining (or Gram's method) is an empirical method of differentiating bacterial species into two large groups ( Gram-positive and Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures In the most common staining technique, the Ziehl-Neelsen stain, AFB are stained a bright red, which stands out clearly against a blue background; therefore, the bacteria are sometimes called red snappers. The Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors Franz Ziehl (1859 to 1926 a bacteriologist and Friedrich [8] The reason for the acid-fast staining is because of its thick waxy cell wall. [9] The waxy quality of the cell wall is mainly due to the presence of mycolic acids. A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural Mycolic acids are long Fatty acids found in the Cell walls of the mycolata Taxon, a group of Bacteria that includes Mycobacterium This waxy cell wall also is responsible for the typical caseous granuloma formation in tuberculosis. Caseous necrosis describes a form of Biological tissue death caseous meaning it has a cheese-like appearance In Medicine ( Anatomical pathology) a granuloma (classical Latin plural granulomata; modern anglicized plural granulomas, also accepted The component responsible, trehalose dimycolate, is called the cord factor. A grading system exists for interpretation of the microscopic findings based on the number of organisms observed in each field. It should be noted that the Ziehl- Neelsen stain is positive in only 50% of cases, which means that, even if no organisms are observed, further investigation is still required. Acid-fast bacilli can also be visualized by fluorescent microscopy using auramine-rhodamine stain for screening, which makes them appear somewhat golden in color. A fluorescence microscope (colloquially synonymous with epifluorescent microscope) is a light Microscope used to study properties of organic or inorganic substances The auramine-rhodamine stain (AR also known as the Truant auramine-rhodamine stain, is a histological technique used to visualizee acid-fast bacilli Also, M. tuberculosis is grown on a selective medium known as Lowenstein-Jensen medium, which has traditionally been used for this purpose. The Lowenstein-Jensen medium, popularly known as LJ medium, is a Growth medium specially used for culture of Mycobacterium, notably Mycobacterium However, this method is quite slow, as this organism requires 6-8 weeks to grow, which delays reporting of results. A faster results can now be obtained using Middlebrook medium.
It should be taken into consideration that during an advanced stage of tuberculosis, the organism may infect almost any part of the body, which means that a specimen should appropriately be chosen (e. g. intestinal tuberculosis-stool).
See also
References
- ^ a b Ryan KJ; Ray CG (editors) (2004). Philip Montagu D’Arcy Hart CBE, ( June 25, 1900 &ndash July 30 2006) was a British medical researcher and pioneer in Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common Sherris Medical Microbiology, 4th ed. , McGraw Hill. ISBN 0-8385-8529-9.
- ^ Cole ST; Brosch R; Parkhill J; et al. (1998). "Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence. ". Nature 393: 537–544. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Camus JC; Pryor MJ; Medigue C; Cole ST. (148). "Re-annotation of the genome sequence of Mycobacterium tuberculosis H37Rv". Microbiology 2002: 2967–2973.
- ^ Murray, P. R. , Rosenthal, K. S. , & Pfaller, M. A. (2005). Medical Microbiology, Elsevier Mosby.
- ^ Vaccines: A souped-up version of BCG, Bell, Nature Reviews Immunology 5, 746, (October 2005)
- ^ http://www.sanger.ac.uk/Projects/M_tuberculosis/
- ^ Microbial Pathogenesis of Mycobacterium tuberculosis: Dawn of a Discipline, Glickman; Jacobs, Cell, Vol 104 Is 4, pg477 - 485
- ^ Flowers T (1995). "Quarantining the noncompliant TB patient: catching the "Red Snapper"". Journal of health and hospital law : a publication of the American Academy of Hospital Attorneys of the American Hospital Association 28 (2): == h == 95-105. PMID 10141473.
- ^ Madigan, Michael; Martinko, John (editors) (2005). Brock Biology of Microorganisms, 11th ed. , Prentice Hall. ISBN 0-13-144329-1.
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