Knowing the pathogenesis of TB, what virulence factors would you expect to see in this microorganism at each stage (main steps) of pathogenesis?

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Practice Question #14 p. 225
Knowing the pathogenesis of TB, what virulence factors would you expect to see in this
microorganism at each stage (main steps) of pathogenesis?
Find the categories of molecules and their function in TB pathogenesis for each
theoretical infection stage as seen in class (exposure, adherence,.)
Steps to pathogenesis
Multiple events, each a limiting barrier for infection, need to occur
before a full-fledged bacterial infections translate into symptoms
and pathology.
The infection process
The disease process
TOXICITY
Toxin effects
are local or
systemic
EXPOSURE
ADHERENCE
INVASION
MULTIPLICATION
Growth and production
of virulence factors
and toxins
TISSUE OR
SYSTEMIC DAMAGE
to pathogens
to skin or mucosa
through epithelium
INVASIVENESS
Further growth
at original and
distant sites
Break in barrier
Transcribed Image Text:Practice Question #14 p. 225 Knowing the pathogenesis of TB, what virulence factors would you expect to see in this microorganism at each stage (main steps) of pathogenesis? Find the categories of molecules and their function in TB pathogenesis for each theoretical infection stage as seen in class (exposure, adherence,.) Steps to pathogenesis Multiple events, each a limiting barrier for infection, need to occur before a full-fledged bacterial infections translate into symptoms and pathology. The infection process The disease process TOXICITY Toxin effects are local or systemic EXPOSURE ADHERENCE INVASION MULTIPLICATION Growth and production of virulence factors and toxins TISSUE OR SYSTEMIC DAMAGE to pathogens to skin or mucosa through epithelium INVASIVENESS Further growth at original and distant sites Break in barrier
It was important for Lilly to understand how the bacteria were able to cause disease in patients.
The mechanism of pathogenesis by M. tuberculosis starts in the lung alveoli. The cell wall of M.
tuberculosis allows it to resist phagocytolysis by the alveolar macrophages, where they can
multiply. They can then induce apoptosis in macrophages, which die, and the bacteria is free to
infect other macrophages. As the cycle of infection slowly progresses, the body's response to the
infection is to try to wall off the bacteria in granulomas (wall of immune cells, both dead and alive,
surrounding the bacteria to restrict its spread). Eventually, the bacteria can escape the granuloma
and infect other parts of the lung.
Transmission of Mtb
Initial infection and
Granuloma cavitation
replication of Mtb
in macrophages
and dissemination
of Mtb in the lung
Infected
macrophages
Caseating
granuloma
Recruitment of
Innate and
adaptive immune
cells
Infected cells undergo
necrosis resulting in
the formation of the caseum
Solid granuloma,
containment of Mtb
Figure 6. Granuloma development during TB progression. The initial stages of TB infection
involve inhalation of M. tuberculosis (Mtb) bacilli into the lung and phagocytosis by resident
alveolar macrophages. Mtb can survive phagocytosis and grow within macrophages for a while.
Once their number reaches a certain threshold and the bacteria has spread locally to other
macrophages, they can elicit a local inflammatory response resulting in the recruitment of
monocytes and macrophages and other immune cells to the site of infection, resulting in the
formation of a granuloma around the infectious agent. This is the balanced solid state in which
many granulomas persist and restrict the bacilli at their center. However, as the disease progresses,
increased necrotic breakdown of granuloma cells leads to the accumulation of caseum (cheese-like
loose collection of dead and live cells), which may result in cavitation of granulomas. Ultimately,
as the granuloma cavitates and collapses into the lung, Mtb bacilli are released into the airway and
can spread to other parts of the lung.
Transcribed Image Text:It was important for Lilly to understand how the bacteria were able to cause disease in patients. The mechanism of pathogenesis by M. tuberculosis starts in the lung alveoli. The cell wall of M. tuberculosis allows it to resist phagocytolysis by the alveolar macrophages, where they can multiply. They can then induce apoptosis in macrophages, which die, and the bacteria is free to infect other macrophages. As the cycle of infection slowly progresses, the body's response to the infection is to try to wall off the bacteria in granulomas (wall of immune cells, both dead and alive, surrounding the bacteria to restrict its spread). Eventually, the bacteria can escape the granuloma and infect other parts of the lung. Transmission of Mtb Initial infection and Granuloma cavitation replication of Mtb in macrophages and dissemination of Mtb in the lung Infected macrophages Caseating granuloma Recruitment of Innate and adaptive immune cells Infected cells undergo necrosis resulting in the formation of the caseum Solid granuloma, containment of Mtb Figure 6. Granuloma development during TB progression. The initial stages of TB infection involve inhalation of M. tuberculosis (Mtb) bacilli into the lung and phagocytosis by resident alveolar macrophages. Mtb can survive phagocytosis and grow within macrophages for a while. Once their number reaches a certain threshold and the bacteria has spread locally to other macrophages, they can elicit a local inflammatory response resulting in the recruitment of monocytes and macrophages and other immune cells to the site of infection, resulting in the formation of a granuloma around the infectious agent. This is the balanced solid state in which many granulomas persist and restrict the bacilli at their center. However, as the disease progresses, increased necrotic breakdown of granuloma cells leads to the accumulation of caseum (cheese-like loose collection of dead and live cells), which may result in cavitation of granulomas. Ultimately, as the granuloma cavitates and collapses into the lung, Mtb bacilli are released into the airway and can spread to other parts of the lung.
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