TOPICS 14 AND 15
Microbiology of C. diphtheriae:
Gram positive, nonsporeforming, nonmotile rods.
Loeffler’s coagulated blood serum
, grows in
Epidemiology of C. diphtheriae
: Humans are the only known reservoir, transmission through
droplets, contact with cutaneous lesions, or fomites.
Diphtheria outbreak in the newly
independent states of the former Soviet Union.
Clinical findings of respiratory diphtheria:
formation beginning in the
tonsils, soft palate, and/or uvula and extending into the nasopharynx, oropharynx, and/or
The extent of pseudomembrane formation correlates with the severity of symptoms.
The pseudomembrane is made of fibrin, dead epithelial cells, RBCs, and WBCs, and will tear
the capillaries and cause bleeding if dislodged.
Cervical lymph nodes will swell and produce a
The diphtheria toxin can spread systemically and especially targets
heart, nerve, and kidney cells, leading to myocarditis, neuropathy, and muscle group paralysis.
Infectious steps for C. diphtheriae:
Transmission via infectious aerosols, from human-to-human contact
Entry into host via respiratory route
iii) Overcomes innate defenses at the mucous membranes:
a. sIgA in mucin layer, viscosity of mucin layer
c. M cells, basolateral pockets, tight junctions
d. MALT, macrophages, dendritic cells
e. Mucociliary escalator, goblet cells
iv) Attachment and colonization- pathogen remains localized, toxin acts both locally and
Acute inflammatory response
b. Increased vasopermeability- leakage of exudate and complement proteins
c. Emigration of phagocytes- margination and diapedesis
d. Chemotaxis- active migration to site of injury via chemokine signals (released by
injured cells), cytokine signals (released by tissue macrophages), and
anaphylotoxins and chemotaxins (C3a and C5a)
f. Formation of fibrin strands
vi) Disease is produced!!