Mycobacterium tuberculosis
Mycobacterium tuberculosis 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 pr…
Why is Mycobacterium tuberculosis considered acid fast?
Microbiological characteristics Mycobacterium tuberculosis is a nonmotile, acid-fast, obligate aerobe. The bacilli are 2-4 um in length and have a very slow generation time of between 15 and 20 hours. The cell wall of the mycobacterium is unique in that it is composed mainly of acidic waxes, specifically mycolic acids.
What are the warning signs of tuberculosis?
M. tuberculosis is a small, rod-shaped, strictly aerobic, acid-fast bacillus 1. Like other mycobacteria, it is slow growing, resulting in more gradual development of disease when compared with other bacterial infections.
Is Mycobacterium tuberculosis armed and dangerous?
Morphology. The Mycobacterium tuberculosis It is a bacterium that belongs to the group of bacilli. They are rod-shaped, and can be straight or slightly curved cells. They are extremely small cells, measuring approximately 0.5 microns wide by 3 microns long.
How does Mycobacterium tuberculosis establish infection?
In this infographic, the genetics, phylogeny, physiology, and pathogenesis mechanisms of Mycobacterium tuberculosis are shown. Mycobacterium tuberculosis is the etiological agent of tuberculosis (TB), the leading cause of death due to a single infectious agent, claiming 1.7 million lives in 2016. Of the deaths attributable to TB in 2016, 22% occurred in people coinfected with …
What makes Mycobacterium tuberculosis special?
In its anatomy, mycobacterium tuberculosis resembles a lot of other bacteria, but it has unique features that make it difficult to diagnose and treat. Its cell wall is extraordinarily thick and complex. A substance called mycolic acid sits on the cell wall and protects the bacillus against the body's immune response.Mar 31, 2016
What characteristic is unique to Mycobacterium?
The distinguishing characteristic of all Mycobacterium species is that the cell wall is thicker than in many other bacteria, being hydrophobic, waxy, and rich in mycolic acids/mycolates.
What is the morphology of Mycobacterium tuberculosis?
Mycobacterium tuberculosis is a fairly large nonmotile rod-shaped bacterium distantly related to the Actinomycetes. Many non pathogenic mycobacteria are components of the normal flora of humans, found most often in dry and oily locales. The rods are 2-4 micrometers in length and 0.2-0.5 um in width.
What is unusual about the cell wall of mycobacteria?
Peptidoglycan is unique to bacterial cells, and it is this property that has led to numerous enzymes involved in its synthesis to be targeted by potent antibiotics, with others representing attractive targets in the development of future antibiotics.
Taxonomy
The taxonomic classification of the Mycobacterium tuberculosis is the next:
Morphology
The Mycobacterium tuberculosis It is a bacterium that belongs to the group of bacilli. They are rod-shaped, and can be straight or slightly curved cells.
General characteristics
The Mycobacteriurm tuberculosis it is a well-known and widely studied bacterium.
Not mobile
This type of bacteria does not show mobility. This is due to the fact that its structure does not present extensions (cilia or flagella) that stimulate its movement.
It is aerobic
Likewise, they are strictly aerobic organisms. Due to this, they must be in an environment in which there is ample availability of oxygen. This is the reason why the main infecting organ is the lung.
It is neither Gram positive nor Gram negative
It cannot be classified as gram positive or gram negative bacteria. Despite containing peptidoglycan in its cell wall, when subjected to Gram staining it does not follow the characteristic patterns of either of the two groups.
They are alcohol-acid fast bacilli
When stained, they are able to resist fading with acid or alcohol, without suffering any structural damage. This is due to the integrity of its cell wall and the role of its components, which makes it more resistant than other types of bacteria.
Why is mycobacterium tuberculosis called a fast bacilli?
This bacterium is difficult to staining but once stained, it becomes resistant to decolorization by diluted mineral acids this is the reason why Mycobacterium tuberculosis is called Acid Fast bacilli (AFB).
What is the genus of Mycobacterium tuberculosis?
Characteristics of Mycobacterium tuberculosis. Mycobacterium tuberculosis belongs to genus Mycobacteria (this is the category M. Tuberculosis in taxonomy). The following characteristics are found in any organism found in this genus.
How many people die from tuberculosis in the world?
There are about 9 million new cases every year and 3 million people die of Mycobacterium Tuberculosis ...
What is culture media?
Solid media. Liquid media. Culture Media is like a broth containing all the needed ingredients for the appropriate growth of specific microorganisms. Because of this, there are different types depending on the ingredient added to it.
How long does it take for mycobacterium tuberculosis to grow?
They grow slowly this is the reason why it takes time to show signs and symptoms of mycobacterium tuberculosis and it also takes time to treat. When culturing mycobacterium tuberculosis, the tubercle colonies appear after 2 weeks or at 6-8 weeks. They are Obligate parasites that depend on others to survive.
How does Mycobacterium tuberculosis spread?
Mycobacterium tuberculosis transmission. Droplet infection: this occurs through person to person transmission by inhalation of aerosols when an infected person coughs, speaks, signs or laughs. Contamination of skin abrasion this occurs mostly in Laboratory workers.
Why are mycobacteria acid fast?
Mycobacteria are classified as acid-fast, due to their reaction to a type of dye called carbolfuchsin. The dye is taken up by the special cell wall of mycobacteria using heat. Then, a decolorizer is applied to strip the stain from any bacteria that do not have the special cell wall.
What degree does Amanda have?
Amanda has taught high school science for over 10 years. They have a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. They also are certified in secondary special education, biology, and physics in Massachusetts. In this lesson we'll be learning about ...
How does tuberculosis spread?
Tuberculosis is easily spread through droplets of saliva in the air, such as when an infected person coughs or sneezes.
What is mycolic acid?
Mycolic acid is a waxy lipid layer that prevents the bacteria from drying out and protects it from harsh environmental conditions. This layer is one of the reasons mycobacteria are difficult to kill. Lesson. Quiz. Course. 4.1K views. Structure of the cell wall and acid fast stain of mycobacteria.
How to diagnose MAC infection?
The best way to diagnose an MAC infection is to culture the bacteria. In immunocompromised patients, samples of sputum, stools, urine or blood are cultured for MAC. Like M. tuberculosis MAC are difficult to grow.
What is the most common blood test?
The most common type of blood test is a interferon gamma release assay ( IGRA). In this test, white blood cells are mixed with proteins from Mycobacterium tuberculosis. If the white blood cells produce a protein called an interferon, the person has the bacteria in their body.
What to do if IGRa is positive?
If the IGRA test is positive, the next step is to do a chest X-ray. The image will reveal if the lungs have white spots where the bacteria are contained. If the chest X-ray is positive the next step is to culture the bacteria. Growing mycobacteria is a challenge because most species have a slow growth rate.
What is the cell wall of M. tuberculosis?
The cell wall of M. tuberculosis is unique in that it has mycolic acids, cord factor, and mAPG complex ( Todar ). Mycolic acids are long fatty acids found in the cell wall of M. Tuberculosis. Because mycolic acids contribute to the waxy-like coating on the cell surface, the bacterial cells are essentially impervious to normal gram staining ...
Is Mycobacterium tuberculosis contagious?
Here is some information regarding the cell structure for Mycobacterium tuberculosis, the cause for the horrid and contagious disease, Tuberculosis! Mycobacterium Tuberculosis has a rod-shape and its a pretty large bacteria!
Is M. tuberculosis a Gram positive or negative?
Interestingly, M. tuberculosis is not classified as either gram positive or gram negative bacteria because it does not have all the characteristics that a gram +/- bacteria would typically have; M. Tuberculosis is considered to be an acid-fast bacteria.
Overview
Microbiology
M. tuberculosis was found in a complex in 2019 that has at least 9 members: M. tuberculosis sensu stricto, M. africanum, M. canetti, M. bovis, M. caprae, M. microti, M. pinnipedii, M. mungi, and M. orygis. It requires oxygen to grow, it is debated whether it produces spores, and is nonmotile. M. tuberculosis divides every 18–24 hours. This is extremely slow compared with other bacteria, which tend to have division times measured in minutes (Escherichia colican divide roughly ever…
Pathophysiology
Humans are the only known reservoirs of M. tuberculosis. A misconception is that M. tuberculosis can be spread by shaking hands, making contact with toilet seats, sharing food or drink, or sharing toothbrushes. However, major spread is through air droplets originating from a person who has the disease either coughing, sneezing, speaking, or singing.
Genome
The genome of the H37Rv strain was published in 1998. Its size is 4 million base pairs, with 3,959 genes; 40% of these genes have had their function characterized, with possible function postulated for another 44%. Within the genome are also six pseudogenes.
The genome contains 250 genes involved in fatty acid metabolism, with 39 of these involved in the polyketidemetabolism generating the waxy coat. Such large numbers of conserved genes show …
Evolution
The M. tuberculosis complex evolved in Africa and most probably in the Horn of Africa. In addition to M. tuberculosis, the M. tuberculosis complex(MTBC) has a number of members infecting various animal species, these include M. africanum, M. bovis (Dassie's bacillus), M. caprae, M. microti, M. mungi, M. orygis, and M. pinnipedii. This group may also include the M. canettii clade. These animal strains of MTBC do not strictly deserve species status, as they are all closely relat…
Antibiotic resistance (ABR)
M. tuberculosis is a clonal organism and does not exchange DNA via horizontal gene transfer. Despite an additionally slow evolution rate, the emergence and spread of antibiotic resistance in M. tuberculosis poses an increasing threat to global public health. In 2019, the WHO reported the estimated incidence of antibiotic resistant TB to be 3.4% in new cases, and 18% in previously treated cases. Geographical discrepancies exist in the incidence rates of drug-resistant TB. Cou…
Host genetics
The nature of the host-pathogen interaction between humans and M. tuberculosis is considered to have a genetic component. A group of rare disorders called Mendelian susceptibility to mycobacterial diseases was observed in a subset of individuals with a genetic defect that results in increased susceptibility to mycobacterial infection.
Early case and twin studies have indicated that genetic components are important in host susce…
DNA repair
As an intracellular pathogen, M. tuberculosis is exposed to a variety of DNA-damaging assaults, primarily from host-generated antimicrobial toxic radicals. Exposure to reactive oxygen species and/or reactive nitrogen species causes different types of DNA damage including oxidation, depurination, methylation, and deamination that can give rise to single- and double-strand breaks (DSBs).