Mycobacterium Tuberculosis I Flashcards
What is the ‘quartet’ of mycobacterium tuberculosis symptoms?
Fever, malaise, weight loss and night sweats
What were the two eras of disease seen with tuberculosis?
Te era of consumption when the bacterial cause of the disease was unknown and the disease was assumed to be hereditary where having the disease was thought to be respectable and enhance creativity and genius
The era of tuberculosis when the bacterial cause of the disease became known and it was no longer ‘fashionable’ to have the disease
What makes mycobacterium tuberculosis an unusual pathogen?
It has a complex lipid cell wall resulting in it not taking up the gram stain instead needing to be stained with an acid fast stain
It grows very slowly replicating only once every 24 hours
Resistant to common antibiotics and lives inside the ‘front line troops’ of the immune system
What are the epidemiological factors of tuberculosis infection?
Most infections are asymptomatic with 10% leading to active infection
Untreated death rate is 50%
Why can mycobacterium tuberculosis be considered a true superbug?
There are 2 biliom people infected and over 8 million new cases each year with 2 million deaths a year
the treatment is difficult and prolonged 2-4 drugs used for 6-18 months
It is highly synergistic with HIV
There is emergence of multi-drug resistance, extremely drug resistant and totally drug resistant
How is mycobacterium transmitted?
Before milk was pastureised mycobacterium bovis could be ingested to cause a non-lung related disease involving the tonsils, cervical lymph nodes and small bowel
It is typically transmitted however through inhalation of respiratory droplets (infectious dose is 5 bacilli)
How can mycobacterium tuberculosis survive inside macrophages?
Its waxy mycolic acid layer resists peroxides
Produces catalase and super oxide disumtases to break down the reactive oxygen and nitrogen species produced by the macrophage
Phagosome maturation is prevented by Protein kinase G which is a eukaryotic-like secreted kinase that blocks delivery of phagosome to lysosome
How does mycobacterium tuberculosis obtain iron in its intracellular environment?
Mycobacterium tuberculosis obtains its iron through production of two high affinity chelaters known as mycobactins, specifically Carboxymycobactin and mycobactin
What is the role of the granuloma in tuberculosis mediated disease?
Initially it was thought that the granuloma was the immune systems way of controlling the infection preventing the bacteria from spreading through the body however there is now evidence to suggest that mycobacterium tuberculosis induces a granulomas as a way of attracting neutrophils to infect and then using these infected neutrophils to disseminate through the body
What evidence suggests that the mycobacterium may be inducing the formation of the granuloma?
Attenuated strains of mycobacterium lack the region of difference RD1 which contains the gene for secreted antigenic target-6 (ESAT-6)
ESAT-6 induces epithelial cells to produce MMP9 which enhances recruitment of macrophages
