Sketchy Microbiology: Mycobacterium Tuberculosis

Shoot out at the TB Corral — Mycobacterium Tuberculosis

Pink Gun w/ pink finish — Acid fast is due to the mycolic acids in membrane that take up dye (Carbol Fuchsin stain) and prevent it from being washed out.

What does “Acid Fast” mean?

It is resistant to acid (Alcohol, Alkali substances)

Lowenstein General Store — Lowenstein Medium needed for culturing

Air Billows Sign — Obligate Aerobe

Jail Cart — Transmission is Human : Human respiratory droplets and proliferates in macrophages

Lasso — Glycolipids are responsible for the clumping of bacteria into a serpentine formation: Virulence factor called cord factor

Lasso Wrapping around driver — Cord factor will Increase granuloma formation by increasing TNF-alpha and cytokines → activating other macrophages → bacteria walls itself off in a granuloma = this will protect the bacteria

Dust clouds behind cowboy — Sulfatides prevent phagolysosome fusion. Allowing TB to survive in macrophages by creating incompetent secondary lysosomes preventing fusion

What are the three stages of a TB infection?

1. Primary Infection

2. Healed Latent Stage

3. Systemic Infection (Miliary TB)

4. Reactivation TB

Left Side ←→ Primary Infection / Healed Latent Stage

Where does the primary infections “reek havoc”?

The Primary infection affects the middle / lower lung lobes

Sick Child in burlap sack — Primary infection symptoms= long fever and in children, resolves by fibrosis (burlap sack)

Cactus with holes in the middle lobe and red cactus fruit = Ghon Complex; visible calcifications of lung parenchyma and hilar lymph nodes

After the Primary infection heals → lung + draining lymph nodes become fibrotic = Ghon Complex

Broken down carts — Caseating Granulomas; tuberculosis resides in broken down necrotic macrophages (Langerhans giant cells)

Shovel with Dirt — Test for TB with PPD, BCG vaccine will always show positive skin test

Millet seed + cow skull — Milliary TB → Multi-organ failure (Lethal)

Guy strapped to barrels of TNF — Latent Infection; Associated with immunosuppression through down regulation of TNF-alpha release.

(Immune system is defenseless if TNF is inhibited. Always screen for PPD before using a TNF inhibitor like infliximab)

Right Side ←→ Reactivated TB

Right Cactus with holes in upper lobe — Reactivation is on the upper lobes of lungs, look for cough, night sweats, Bloody cough (hemoptysis)

Guy Inside Barred Cart — Reactivation occurs from inside the macrophages

Coughing out blood on handkerchief — Cachexia / wasting away is common

Broken Pots — Pots disease is the demineralization of the bones → spinal weakness

Bullet hole going through the hat — CNS involvement is also seen as meningitis or tuberculoma

Treatment for TB: RIPE

Rifampin

Isoniazid

Pyrazinamide

Ethambutol

Hint: R and I are brown

Prophylaxis — Rifampin or Isoniazid for 9 months

Other than Mycobacterium Tuberculosis, what other entities exist?

• Non-Tuberculotic mycobacterial infections

• Leprosy

• Saprophytes