Corynebacteria are gram-positive, non-motile, non-capsulated, and non-spore forming bacilli that appear club-shaped under microscopy. Important species include C. diphtheriae, which causes diphtheria, an acute infectious throat disease. Diphtheria toxin produced by C. diphtheriae inhibits protein synthesis and causes membrane formation in the throat. Treatment involves antitoxin and penicillin. Actinomycetes are filamentous, anaerobic, gram-positive bacteria that resemble fungi and can produce sulfur granules, while the related Nocardia are aerobic, filamentous, and weakly acid-fast bacteria that are opportunistic

1. Corynaebacteria

2. Corynaebacteria
Greek = Korune = Club
Club is a stout stick with a thickened end
 Gram positive bacilli
 Non motile
 Non capsulated
 Non spore forming

3. Corynaebacteria Species
 C. diptheriae
 C. xerosis
 C. ulcerans
 C. jeikeium
 C.urealyticum

4. Morphology
 Gram stain: Club shaped, arranged in
Chinese letter or Palisading
arrangement
 Albert stain: Metachromatic i.e. the
bacillus is blue/Green and the granules
are red. (the granules are high energy
phosphate bonds).

5. Culture
 Blood agar
 Blood agar with Tellurite
 Loeffler’s serum slope agar
 Types: Gravis, intermedius, mitis and
belfanti

7. Diphtheria
Greek - Rubber membrane
An acute infectious disease chiefly of
children caused by C. diptheriae and
characterized by severe inflammation of
the throat, heart and nervous system. (It
is preventable by inoculation)

8. Diptheria
 Caused by C. diptheriae possessing
toxin
 Exotoxin with MW 62000
 Has two subunits A and B
 Carried on a Bacteriophage

9. Diptheria Toxin
Mechanism of Action:
Causes inhibition of protein synthesis in
cell by inhibition of Elongation Factor
(EF) 2

10. Diptheria Toxin Actions
 Local: Severe inflammation of the
mucous membranes of the pharynx,
nasopharynx and larynx leading to
“Pseudomembrane” formation.
 Distant: Heart and Nervous system

11. Diptheria Pseudomembrane
 Gray Colour
 Necrotic epithelial cells embedded in
fibrin strands, white and red blood cells.
 Attempt to remove it exposes
underlying capillaries and causes
bleeding. This can lead to absorption of
the toxin.

16. Treatment
 Circulating Toxin Antitoxin
 Organisms Penicillin

17. Actinomycetes
 Group of filamentous anaerobic Gram
positive bacteria
 Resemble fungi superficially
 Free living
 A. israelii is part of the normal flora of
mouth and intestine
 Produce pus resembling sulphur
granules

18. Nocardia
 Aerobic filamentous bacteria
 Acid fast with 1 % sulphuric acid
 Soil organisms
 Cause opportunistic infections
 Infection follow their inhalation

19. Comparison
Antinomycetes
 Filamentous
 Gram +
 Non acid fast
 Anaerobic
 Sulphur granules
 Actinomycocis
 Treatment Penicillin
 A. israelii
Nocardia
 Filamentous
 Stain unevenly(Gram +)
 Weak acid fast
 aerobic
 No sulphur granules
 Nocardiosis
 Sulphamethoxazole
 N.asteroides