Question

Medical Microbiology Tutorial: Bacterial Infections. Tuberculosis and Staphylococcus aureus

Answer 1

note: I'm only grouping these two together because they're both bacterial infections, and I don't have enough content to make them both separate tutorials

Answer 2

\({\bf{Tuberculosis:}}\)


caused by: Mycobacterium tuberculosis
transmission: airborne

Brief History:
- 1869: Jean Antonie Villemin demonstrates that TB is an infectious disease, showed that injecting TB-infected tissue from animals could cause TB in humans
- late 1880's: Robert Koch isolates the bacteria that causes TB and develops tuberculin from TB extract (not successful at preventing TB)
- 1908-1921: development of BCG vaccine by Albert Calmette and Camille Guérin. typically not used in the United States since TB is pretty rare here

Latent vs Active:
There are two stages, the latent and active stages.
The latent stage is asymptomatic and non-contagious. Can be diagnosed w/ TB skin test and blood tests but x-ray scans appear normal. If detected, is recommended to be treated.

The active stage does show symptoms and is contagious. TB skin tests, blood tests, phlegm tests are positive, plus x-ray scans appear abnormal.

Symptoms:
As stated before, these typically only show up in active stage.
- weight loss
- loss of appetite
- fever
- chills/night sweats

Treatment:
- medications such as Isoniazid, Rifampicin, Pyrazinamide, Ethambutol
- open-air treatment
- untreated latent TB goes on to become full-blown TB in about ~10% of cases

Answer 3

\({\bf{Staphylococcus~aureus:}}\)
- most common drug-resistant pathogen
- MRSA: methicilin-resistant S. aureus is the most commonly known one, and of great concern to researchers and medical professionals
> MRSA are resistant to beta-lactams like penicillin. MRSAs contain beta-lactamase which cleaves rings in beta-lactams, making them ineffective
- causes a wide variety of diseases/ailments ranging from skin conditions like boils or impetigo, to more serious conditions like toxic shock, pneumonia, meningitis, and sepsis

treatments: antibiotics such as clindamycin, minocycline, doxycycline

Features: these are mostly designed to get around the host immune system and proliferate
- adhesins: bind to host surface cell receptors + complement factors, can inhibit complement activation cascade, interferes w/ immune responses
- leukocidins: toxins that kill host cells
- immunoglobin binding proteins: bind to host immunoglobins
- autolysins: break down old peptidoglycan so new peptidoglycan can be formed and bacterial growth can occur
- proteases: target and cleave host immunoglobins
- superantigens: activate T cells and cytokine release

Answer 4

Sources:
- https://www.cdc.gov/hai/organisms/staph.html
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3971415/
- https://www.cdc.gov/tb/publications/factsheets/general/ltbiandactivetb.htm
- https://www.britannica.com/biography/Jean-Antoine-Villemin
- https://www.cdc.gov/tb/education/corecurr/pdf/chapter2.pdf
- https://www.cdc.gov/tb/topic/testing/default.htm#targetText=A%20positive%20TB%20skin%20test,the%20person%20has%20TB%20disease.
- lecture notes