Mycobacteria- summary.docx

3 Pages
Unlock Document

Western University
Microbiology and Immunology
Microbiology and Immunology 2500A/B
John Mc Cormick

Mycobacteria- TB and Leprosy M. tuberculosis- causes TB in humans (humans are only reservoir) - called TB because of Tubercle bacilli (form tubercles) M. bovis- causes TB in cows - rare in humans- but can thru unpasteurized milk → extrapulmonary TB M. avium- causes TB-like illness in humans (mainly AIDS patients) M. Leprae- causes leprosy M. tuberculosis - Facts- 2 largest killer (by infectious disease) - 1/3 of pop’n has org in them (2 bill) - 1 of 10 of these will develop active TB (10% develop) - The pathogen- Robert Coch in 1882 - obligate human pathogen- only lives in us - intracell. pathogen- in macrophages - non motile, rod, obligate aerobe (need O2) - long generation time- 15h, takes 4-6 weeks for small colonies in lab - Mycobacteria- high mycolic acid in cell envelope - resist antibiotics, acid/base, lysis by complement, oxidative stress (can live in macrophage) - impermeable to stains (cant use gram stain) - acid fast stain: very waxy envelope 1. Stain with basic dye (carbolfuschin) with heat to melt wax 2. wash with EtOH + HCl 3. counterstain methylene blue → acid fast mycobact. are red while the rest are blue 4 stages of TB 1. Transmission = inhale sneezed droplets (w bacteria) directly into lung (finer = longer suspended) 2. 7-21 days after initial exposure - alveolar macrophage engulf TB → TB multiplies in unactivated macrophages → lyse and spread - key virulence factor- ability to survive in macrophages (stops phagosome & lysosome fusion) 3. Granulomas (tubercles)- made of macrophages and Tcells - balance between pathogen and host → latent infection (lasts for years) - macrophages in center are harder to activate by Tcells (activated ones can kill TB and present) - caseous necrosis (cheese like)- dead cells 4. Tubercle grows- some macrophages remain unactivated - erosion = get into airway = transmission - bad host immune system → active TB (actively coughing and transmitting) - caseuos center can liquefy and explode → cavitation 75% is pulmonary (contagious) 25% is extra pulmonary (non-contagious) - Irreversible lung damage - More in immunocompromised ppl - Latent carriers cannot transmit - Infects- bone, liver, GI tract, brain- anything - Single bacterium can cause - Systemic spread- military TB (seeds)→ fatal TB Symptoms - Thick, bloody cough/mucus, fever, chills, fatigue, weakness, chest pain, SOB - Loss of appetite, weight loss- “consumption” - Pallor (paleness)- “white death” Diagnosis - Tuberculin test- PPD (purified protein derivative
More Less

Related notes for Microbiology and Immunology 2500A/B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.