Etiology
Corynebacterium diphtheriae
This organism appears as gram-positive shaped rods arranged in V or L forms due to snapping division.
This cellular process is inhibited by diphtheria toxin.
Protein synthesis
Characteristic throat lesion seen in diphtheria
Gray pseudomembrane
Best initial sample
Throat swab
This neutralizes circulating toxin
Diphtheria antitoxin
Toxin production in this organism depends on infection by this genetic element.
Lysogenic bacteriophage (β-phage)
The toxin acts by ADP-ribosylation of this factor.
EF-2
This sign indicates severe disease and airway risk
Bull neck
This medium gives black colonies due to tellurite reduction
Tellurite agar
These antibiotics eliminate carriage (name one)
Penicillin / Erythromycin
Only strains possessing this gene can cause systemic complications.
tox gene
The pseudomembrane is composed of these components (name at least 2).
Fibrin, dead cells, bacteria, inflammatory cells
Cranial nerve involvement leads to this symptom
Dysphagia / nasal speech
Test used to detect toxin production
Elek test
Why can’t antibiotics alone prevent complications?
They do not neutralize toxin
A throat culture grows the organism, but the patient has no systemic symptoms. What property must be confirmed next?
Toxigenicity (toxin production)
Why does removing the membrane cause bleeding?
It is tightly adherent to necrotic tissue
A patient has fever, tonsillar exudate, and lymphadenopathy. What feature favors diphtheria over streptococcal pharyngitis?
Adherent membrane that bleeds
PCR detects the gene, but what must still be confirmed clinically?
Active toxin production
Before giving antitoxin, this test should be considered due to its origin
Hypersensitivity (skin test for horse serum)
Why are some carriers asymptomatic despite colonization?
Infection with non-toxigenic strains
A patient develops cardiac arrhythmia 2 weeks after sore throat recovery. What is the mechanism?
Toxin-mediated myocardial damage
A child has mild fever but severe toxicity. Why is fever low despite serious illness?
Disease is toxin-mediated, not inflammatory
A suspected case presents in emergency. Lab results are pending. What is your next step?
Start antitoxin immediately
What is the most important factor determining prognosis?
Timing of antitoxin administration