HRR: mycobacterial infection Flashcards
What are the general characteristics of mycobacteria?
They’re non-motile obligate aerobes that do not form spores. They have complex cell walls with a bunch of peptidoglycans, lipids, and polysaccharides.
What are some lipids found in mycobacteria cell walls?
Mycolic acids and lipoarabinomannan.
What does the cell wall do for mycobacteria?
Makes them poorly penetrable; they’re like hard balls of wax.
What is the staining property of mycobacteria?
Acid fast.
What determines whether a disease develops following human exposure to mycobacteria?
The pathogenicity of the species and the person’s immune system.
What is the leading infectious disease killer?
TB.
How is TB spread?
Person to person.
TB is normally a ___ presentation.
Subacute.
Why is TB difficult to treat?
It requires multiple months of multiple antibiotics, and may become resistant to antibiotics.
What is the time frame for tuberculosis growth?
3-4 weeks in culture.
Tuberculosis is resistant to…
Disinfectant and drying.
What is tuberculosis sensitive to?
Heat.
What features allow tuberculosis to hang out in the air?
Their droplet nuclei are resistant to drying; this is partly a function of their waxiness.
What is the primary manifestation of TB?
Pulmonary disease; it often forms cavity lesions in the upper lobe and apical region. These cavities have billions of mycobacteria.
Who is more likely to develop cavities with TB: immunocompetent or immunocompromised?
Immunocompetent! The immunocompromised don’t develop the cavities.
What is TB spondylitis?
It is typically found in children and causes an anterior wedging of the spine.
Describe TB meningitis.
Happens in young kids or the immunocompromised. Can pick off cranial nerves and is highly inflammatory. It is diagnosed by lumbar puncture and imaging.
What is an implication of GU TB?
Infertility.
GI TB can mimic which condition?
Crohn’s disease.
If someone is infected with TB, what routes are possible?
Most people’s immune system can control TB and prevent them from being sick; the TB will remain latent. The other options include progressive primary/early disseminated TB in which the person becomes sick within 1-2 years following exposure, or reactivation TB in which someone gets sick years later.
Describe the process of infection with progressive primary TB.
- We breathe in bacteria, which then travel to the alveoli and are not killed by macrophage. 2. There is a lack of control by the innate response. 3. The bacteria invade interstitial lung tissue. 4. Dendritic cells transport bacteria to lymph nodes and there is T and B cell recruitment. 5. The acquired immune response is unable to control the infection, and progressive primary TB occurs.
Describe the process of controlling TB infection.
- We breathe in bacteria, which travel to the alveoli and are not killed by macrophages. 2. The innate immune response, T cells, and B cells control the infection within granulomas. 3. You continue with latent infection, unless a lack of control causes reactivation TB.
Describe the composition of granulomas in TB.
A caseous center of bacteria surrounded by a layer of activated macrophages and an outer layer of T and B cells.
What cytokines are important for maintaining granulomas and preventing them from breaking open and causing issues?
IFN-gamma, IL-12, TNF-alpha.
