1. MYCOBACTERIA CORYNEBACTERIA Lecture 40
Faculty: Dr. Alvin Fox

2. KEYWORDS Acid Fast Tuberculosis (TB) M. tuberculosis (MDR, XDR)
M. avium - M. intracellulare complex
M. bovis
M. leprae
Tubercle
PPD
Tuberculin
Mycobactin
Cord factor
BCG
Leprosy (Hansen's Disease)
AIDS and TB
Runyon groups
Mycolic acids
Diphtheria
C. diphtheriae
Loeffler's agar
Tellurite agar
Metachromatic bodies
Diphtheria toxin
Schick test
Diphtheroids

3. Mycobacterium tuberculosis
obligate aerobe
acid-fast rods

4. Tuberculosis (TB, consumption) M. tuberculosis major human disease
healthy people
problems
association with AIDS
multiple drug-resistance

5. M. avium- M. intracellulare complex (M. avium)
non-AIDS
infection almost never
AIDS
major bacterial opportunist
multiple drug-resistance

6. M. bovis
spread from cattle
infected cattle are culled
positive skin test
rarely seen in US

7. M. leprae
leprosy
major disease of third world
rare in US

8. Transmission -tuberculosis
M. tuberculosis causes disease
healthy individuals
transmitted man-man
airborne droplets

9. Pathogenesis of tuberculosis
infects lung
distributed within macrophages
facultative intracellular pathogen
inhibits phagosome-lysosome fusion

10. Cell-mediated immunity -tuberculosis
infiltration
macrophages
lymphocytes
granulomas
tubercules

11. Laboratory diagnosis - tuberculosis
skin testing
delayed hypersensitivity
tuberculin
protein purified derivative, PPD
X-ray

12. Positive skin test -tuberculosis
indicates exposure to organism
does not indicate active disease

13. tuberculosis Other minor pathogenesis factors mycobactin siderophore
cord factor
damages mitochondria

14. Laboratory diagnosis M. tuberculosis
acid fast bacteria
sputum

15. Laboratory diagnosis M. tuberculosis (culture)
grows very slowly
two weeks or longer
non-pigmented colonies
niacin production
differentiates from other mycobacteria

16. Tuberculosis
polymerase chain amplification
rapid diagnosis

17. Antibotic treatment - tuberculosis
extensive time periods (e.g. 9 months)
organism grows slowly, or dormant
two or more antibiotics
e.g. rifampin and isoniazid
resistance minimized

18. Tuberculosis and Drug resistance
Multiple drug resistant (MDR)
resistant to first line drugs
Extremely drug resistant (XDR)
Resistant to some of the second line drugs
Nearly un-treatable

19. Vaccination BCG vaccine an attenuated strain of M. bovis not effective
in US,
incidence is low
vaccination not practiced
immunization interferes with diagnosis

20. Mycobacterium leprae

21. Leprosy (Hansen's Disease)
M. leprae
causative agent
chronic disease
disfigurement
rarely seen in the U.S.
common in third world
- effective antibiotic therapy recently initiated, incidence way down
infects the skin
low temperature

22. ulcers, resorption of bone
worsened from careless use of hands (nerve damage)

23. Leprosy tuberculoid few organisms active cell-mediated immunity
lepromatous
many organisms
immunosuppression

24. Production of M. leprae antigens and
pathogenesis studies
in vitro
unculturable
in vivo growth
low temperature
armadillo (laboratory and native [e.g. TX])
mouse footpad

25. Leprosy lepromin skin testing acid-fast stains skin biopsies
clinical picture

26. Other mycobacterial species (including M. avium)
infect immunocompromised host
not transmitted man-man, healthy people
M. avium – common
Other species - rare

27. Mycobacterial diseases
tuberculosis-like
leprosy-like

28. M. avium is much less virulent than M. tuberculosis
Mycobacteria and AIDS
M. avium is much less virulent than M. tuberculosis
does not infect healthy people
infects AIDS patients
M. avium infects
when CD4 (helper T cell) count greatly decreased
M. tuberculosis infection
infects healthy people
earlier stage of disease
more systemic

29. Clinical features with AIDS
systemic disease (versus pulmonary)
greater in AIDS
lesions often lepromatous

30. Antibiotic therapy
selected primarily for M. tuberculosis
if M. avium involved other antibiotics included

31. Other species pigmented or not pigmentation in the light in the dark
growth
fast
slow

32. Mycobacterial species identification
cellular fatty acid profiles
mycolic acid profiles
genetic markers

33. Mycolic acids mycobacteria longest chain length strongly acid fast
nocardia
intermediate chain length
weakly acid fast
corynebacteria
shortest chain length
not acid fast

34. Corynebacterium diphtheriae
Gram positive
strict aerobe
pleomorphic (e.g. club-shaped)

35. Diphtheria member of normal flora of pharynx
overgrowth upper respiratory tract
pseudomembrane
chocking
bacteria do not spread systemically
The toxin does disseminates .

36. This child has diphtheria resulting in a thick gray
coating over back of throat. This coating can
eventually expand down through airway and, if not
treated, the child could die from suffocation CDC

37. Diptheria toxin
spreads
systemic and fatal injury

38. Diphtheria toxin B binds to host cell A inhibits protein synthesis
ADP-ribose moiety (NADH) attaches
elongation factor 2 inhibited

39. Treatment
anti-toxin
antibiotic

40. Immunization against diphtheria (infant)
disease vanished in US
without immunization will return
toxoid (+ pertussis and tetanus) DPT
neutralizing antibodies
colonization not inhibited
found in normal flora

41. Testing immunity
Schick skin test
toxin

42. Diphtheria toxin coded by bacteriophage tox gene
not synthesized if iron present
iron-repressor complex forms
inhibits expression of tox gene

43. Identification - C. diphtheriae
growth Loeffler's medium
stain for polyphosphate granules
metachromatic
polyphosphate granules (pink) cell (blue)
tellurite agar
reduction by bacteria
tellurium precipitation
black colonies

44. Identification – Exotoxin production
in vivo
in vitro

45. C. diphtheriae should not be confused with:
diphtheroids
other corynebacteria
propionibacteria