Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is an infectious disease usually caused by Mycobacterium tuberculosis (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in which case it is known as latent tuberculosis. Around 10% of latent infections progress to active disease which, if left untreated, kill about half of those affected. Typical symptoms of active TB are chronic cough with blood-containing mucus, fever, night sweats, and weight loss. Infection of other organs can cause a wide range of symptoms.
Mycobacterium tuberculosis, also known as Koch's bacillus, is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. 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. This coating makes the cells impervious to Gram staining, and as a result, M. tuberculosis can appear weakly Gram-positive. Acid-fast stains such as Ziehl–Neelsen, or fluorescent stains such as auramine are used instead to identify M. tuberculosis with a microscope. The physiology of M. tuberculosis is highly aerobic and requires high levels of oxygen. Primarily a pathogen of the mammalian respiratory system, it infects the lungs. The most frequently used diagnostic methods for tuberculosis are the tuberculin skin test, acid-fast stain, culture, and polymerase chain reaction.
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 and leprosy in humans. The Greek prefix myco- means 'fungus', alluding to this genus' mold-like colony surfaces. Since this genus has cell walls with a waxy lipid-rich outer layer that contains high concentrations of mycolic acid, acid-fast staining is used to emphasize their resistance to acids, compared to other cell types.
Mycobacterium leprae is one of the two species of bacteria that cause Hansen’s disease (leprosy), a chronic but curable infectious disease that damages the peripheral nerves and targets the skin, eyes, nose, and muscles.
Isoniazid, also known as isonicotinic acid hydrazide (INH), is an antibiotic used for the treatment of tuberculosis. For active tuberculosis, it is often used together with rifampicin, pyrazinamide, and either streptomycin or ethambutol. For latent tuberculosis, it is often used alone. It may also be used for atypical types of mycobacteria, such as M. avium, M. kansasii, and M. xenopi. It is usually taken by mouth, but may be used by injection into muscle.
Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), Mycobacterium avium complex, leprosy, and Legionnaires' disease. It is almost always used together with other antibiotics with two notable exceptions: when given as a "preferred treatment that is strongly recommended" for latent TB infection; and when used as post-exposure prophylaxis to prevent Haemophilus influenzae type b and meningococcal disease in people who have been exposed to those bacteria. Before treating a person for a long period of time, measurements of liver enzymes and blood counts are recommended. Rifampicin may be given either by mouth or intravenously.
Tuberculosis is diagnosed by finding Mycobacterium tuberculosis bacteria in a clinical specimen taken from the patient. While other investigations may strongly suggest tuberculosis as the diagnosis, they cannot confirm it.
Pyrazinamide is a medication used to treat tuberculosis. For active tuberculosis, it is often used with rifampicin, isoniazid, and either streptomycin or ethambutol. It is not generally recommended for the treatment of latent tuberculosis. It is taken by mouth.
4-Aminosalicylic acid, also known as para-aminosalicylic acid (PAS) and sold under the brand name Paser among others, is an antibiotic primarily used to treat tuberculosis. Specifically it is used to treat active drug resistant tuberculosis together with other antituberculosis medications. It has also been used as a second line agent to sulfasalazine in people with inflammatory bowel disease such as ulcerative colitis and Crohn's disease. It is typically taken by mouth.
Mycolic acids are long fatty acids found in the cell walls of Mycobacteriales taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of many Mycobacteriales species. Despite their name, mycolic acids have no biological link to fungi; the name arises from the filamentous appearance their presence gives Mycobacteriales under high magnification. The presence of mycolic acids in the cell wall also gives Mycobacteriales a distinct gross morphological trait known as "cording". Mycolic acids were first isolated by Stodola et al. in 1938 from an extract of M. tuberculosis.
Tuberculous meningitis, also known as TB meningitis or tubercular meningitis, is a specific type of bacterial meningitis caused by the Mycobacterium tuberculosis infection of the meninges—the system of membranes which envelop the central nervous system.
A mycobacteriophage is a member of a group of bacteriophages known to have mycobacteria as host bacterial species. While originally isolated from the bacterial species Mycobacterium smegmatis and Mycobacterium tuberculosis, the causative agent of tuberculosis, more than 4,200 mycobacteriophage have since been isolated from various environmental and clinical sources. 2,042 have been completely sequenced. Mycobacteriophages have served as examples of viral lysogeny and of the divergent morphology and genetic arrangement characteristic of many phage types.
Mycobacterium vaccae is a nonpathogenic species of the Mycobacteriaceae family of bacteria that lives naturally in soil. Its name originates from the Latin word, vacca (cow), since the first Mycobacterium strain was cultured from cow dung in Austria. Mycobacterium vaccae was first isolated from the Ugandan Lang'o District, where locals claimed that a "muddy substance had the power to cure a number of ailments". Research areas being pursued with regard to killed Mycobacterium vaccae vaccine include immunotherapy for allergic asthma, cancer, depression, leprosy, psoriasis, dermatitis, eczema and tuberculosis.
ESAT-6 or Early Secreted Antigenic Target 6 kDa, is produced by Mycobacterium tuberculosis, it is a secretory protein and potent T cell antigen. It is used in tuberculosis diagnosis by the whole blood interferon γ test QuantiFERON-TB Gold, in conjunction with CFP-10.
Thiocarlide is a thiourea drug used in the treatment of tuberculosis, inhibiting synthesis of oleic acid and tuberculostearic acid.
Isocitrate lyase, or ICL, is an enzyme in the glyoxylate cycle that catalyzes the cleavage of isocitrate to succinate and glyoxylate. Together with malate synthase, it bypasses the two decarboxylation steps of the tricarboxylic acid cycle and is used by bacteria, fungi, and plants.
In enzymology, a β-ketoacyl-[acyl-carrier-protein] synthase III (EC 2.3.1.180) is an enzyme that catalyzes the chemical reaction
In enzymology, a malate synthase (EC 2.3.3.9) is an enzyme that catalyzes the chemical reaction
PncA is a gene encoding pyrazinamidase in Mycobacterium species. Pyrazinamidase converts the drug pyrazinamide to the active form pyrazinoic acid. There is a strong correlation between mutations in pncA and resistance of M. tuberculosis to pyrazinamide.
François Balloux is the director of the UCL Genetics Institute, and a professor of computational biology at University College London.
