11:680:390 Lecture Notes - Lecture 23: Corynebacterium Diphtheriae, Necrotizing Fasciitis, Mycobacterium Tuberculosis
26 Apr 2018
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23: Person-to-Person Diseases
I. Bacterial Diseases
A. Strep Throat: bad tonsil infections
1. Caused by Streptococcus pyogenes (white appearance on throat)
a) Group A: infection in upper respiratory tract; common in throats of
healthy individuals
b) Group B: possibly in vagina of females, can be a healthy carrier;
can be transmitted to baby at birth and can cause meningitis
2. Properties
a) hemolysins - cytolytic toxin (streptolysin)
b) capsules = invisibility cloak
c) Streptokinase
3. Causative agents: infections of the inner ear, mammary glands, and skin
as impetigo
4. Infections occur if host defenses are weakened or a new, highly virulent
strain is introduced
5. Certain group A strains carry a lysogenic bacteriophage that encodes
exotoxins responsible for symptoms of streptococcal toxic shock
syndrome and scarlet fever
6. Necrotizing fasciitis
- flesh eating disease
B. Diphtheria
1. Caused by Corynebacterium diphtheriae
2. Preventable and treatable
3. Spreads by airborne droplets and enters body via respiratory route
4. Previous infection or immunization provides resistance
5. Produces exotoxins that cause
a) Tissue death due to prevention of protein synthesis
b) Growth of a pseudomembrane in patients throat
6. 99% mortality rate
C. Pertussis (whooping cough)
1. Caused by Bordetella pertussis
2. Observed frequently in school-age children
3. Consistent upward trend since 1980s because decreased number of
vaccines, the microbe strain has changed, and the vaccine isn’t as
effective.
D. Tuberculosis
1. Caused by Mycobacterium tuberculosis
- WHO estimates ~⅓ of world’s
population is infected
2. Latent TB - no symptoms, not infectious; can become TB disease
3. TB Disease - sick & infective; TB bacteria become active if the immune
system can’t contain them
4. Tubercles - secretes something that creates spots in your lungs (can be
picked up by x-rays)
