Mycobacterium tuberculosis strain H37Rv is the most studied

strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...

of tuberculosis in research laboratories. It was first isolated by Dr. Edward R. Baldwin in 1905. The strain came from a 19 year old patient with chronic pulmonary tuberculosis at the Trudeau Sanatorium in

Saranac Lake, New York Saranac Lake is a village in the state of New York, United States. As of the 2010 census, the population was 5,406, making it the largest community by population in the Adirondack Park. The village is named after Upper, Middle and Lower Saran ...

. It was maintained for many years by

serial passage Serial passage is the process of growing bacteria or a virus in iterations. For instance, a virus may be grown in one environment, and then a portion of that virus population can be removed and put into a new environment. This process is repeated ...

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at the Trudeau Sanatorium and initially named strain H37. Over time it was found to have variable virulence in animal models based on which

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it was grown on. Strains with different

virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to ...

were then intentionally produced, with H37R being less virulent after growing in acidic media and H37S was more virulent in guinea pigs after being grown in alkaline media (with R standing for resistant to environment, and S for sensitive to environment). The more virulent strain was later renamed H37Rv, with R standing for rough

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and v standing for virulent. The strain was used for many laboratory studies and became the standard for tuberculosis. It was later designated as the

neotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

for the species. Koch first discovered mycobacterium tuberculosis as the cause of

tuberculosis Tuberculosis (TB) 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, i ...

in 1892 but the strains he studied were not preserved and it is unclear how related H37Rv may be to those strains. H37Rv has continued to be the strain of tuberculosis most used in laboratories, and was the first to have its complete

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...

published in 1998. 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 century grave in

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. However it does not have some characteristics, such as causing

caseous necrosis Caseous necrosis or caseous degeneration () is a unique form of cell death in which the tissue maintains a cheese-like appearance.Robbins and Cotran: Pathologic Basis of Disease, 8th Ed. 2010. Pg. 16 It is also a distinctive form of coagulative nec ...

in rabbits, that are seen in modern clinical isolates. Strains in different labs that derive from H37Rv have also been shown to have evolved differences over time, with one survey of 6 strains finding from 5 to 10 polymorphisms per strain. These included independent insertions and deletions of IS6110

transposable element A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transp ...

s which would change the strain's spoligotype. The authors of the study cautioned against considering all strains labeled as H37Rv as a reference since there may be significant differences based on the laboratory in which it is maintained.

References

{{Medicine, state=collapsed Tuberculosis *H