Diphtheria Flashcards
What is the gram, size, and shape of Corynebacteria? Aerobe? Spore forming?
Pleomorphic, G+ rods, aerobic, no spores
What are the two categorical groups of Corynebacteria?
Corrnebacterium Dipththeriea (casuses diphtheria)
All other Corynebacteria, called diphtheroids, which are normal inhabitants to our skin and throat.
What is the signature feature of gram stained Corynebacteria?
Looks like chinese characters
How long does the diphtheria vaccine work?
Confers immunity for 10 years
What animals are hosts for Diptheria?
What is transmission mode?
Only Humans
Respiratory droplets (anywhere) and necrotizing skin infection spread by contact (tropics only)
What is the incubation period for Diphtheria?
2-5 days
What is the histological feature of Diphtheria infected tissues?
pseudomembrane composed of fibrin, necrotic epithelium, and WBCs
Does Diphtheria cause systemic infection?
No. It is confined to its initial focus in the throat or skin
If Diptheria is a local infection, how does it cause systemic symptoms?
Secretion of exotoxin
To what tissues is Diphtheria toxin damaging or fatal?
Lethal to all eukaryotic cells
Fatal if affects heart, kidney, or nervous system
What is the source of the Diptheria toxin gene?
Originated in a bacteria phage. This is a case of “lysogenic conversion.” Discussed in a later class.
Explain the endocytosis and effect of Diphtheria toxin into cells.
Diphtheria toxin has two domains.
Domain B binds to cell surface receptors and caused endocytosis.
Domain A is extruded from the endosome into the cell.
Domain A blocks EF2 elongation factor and hence blocks protein synthesis
What is the initial “tentative” diagnosistic technique for Diphtheria?
Characteristic growth on Tellurite agar, Tinsdale’s medium, and Leoffler media.
Metachromatic granules can be visualized.
What are the three methods of “definitive” diagnosis?
All three demonstrate Diphtheria Toxin
Elek Test
PCR Test
Immunoassay
Wha is the Elek test?
On agar, single streak of bacteria that perpendicularly bisects antitoxin paper.
A line of precipitate forms on the line Y = X
See page M-7 for details
