Diphtheria Overview and Clinical Findings

Study Notes

Classified as a childhood bacterial disease, incidence rate low due to vaccination programs
Gram-positive, club-shaped bacteria, forming various shapes (e.g., letter-like/L-forms)
Contains metachromatic granules that store energy (visible when stained with methylene blue)
Three species: C. diphtheriae gravis, C. diphtheriae mitis
Transmission: Respiratory droplets and direct contact; also, occurs in the upper respiratory tract
Risk factors: Unvaccinated children, incomplete doses of vaccination, immunocompromised individuals (e.g., using corticosteroids long-term), or those with chronic conditions, transplant recipients.
Pathogenesis: Bacteria invade, multiply locally, producing a potent exotoxin. The exotoxin is a major cause of disease pathology.

Incubation period: 2-6 days
Commonly affected sites: Tonsils, soft palate, larynx, nose.
Characteristic feature: Formation of a thick, gray pseudomembrane on tonsils/throat.
Other clinical signs: Dirty brown/green discolouration, inflammatory exudate, leukocytes, fibrin, and desquamated epithelial cells.
Membranes are difficult to dislodge. Dislodging causes bleeding from the underlying tissues.
Additional clinical findings: Fever, sore throat, cervical lymphadenopathy (bilateral swelling of lymph nodes in the neck), bull-neck appearance (a characteristic facial feature).

Airway obstruction due to membrane formation
Myocarditis, causing arrhythmias and shock
Neurological issues: Weakness, paralysis
Rarely: Perforation of the soft palate, allowing food to enter the infection site (potentially causing infection).

Specimen: Throat swab
Gram stain: Observing tapered, pleomorphic gram-positive rods, and metachromatic granules
Culture: Löffler's medium or tellurite blood agar for growth observation of gray-black colonies.
Toxin production test: Elek's test for identification
Animal inoculation test: testing for toxin production-

Treatment of choice: Antitoxin (toxoid) (20,000-100,000 units intravenously)
Prior hypersensitivity testing on forearm to evaluate the potential reaction prior to full dose administration, using a small initial dose.
Treatment timing: Immediate, based on clinical suspicion.
Alternative agents: Erythromycin as an alternative for those with penicillin allergies.

Diphtheria toxoid: Prepared by treating the toxin with formalin.
Combined vaccine: Diphtheria toxoid, tetanus toxoid, and acellular pertussis vaccine (DPT).
Vaccination schedule: Three doses at one-month intervals, starting from 45 days after birth.
Importance: Regular vaccinations are crucial for disease prevention.