Key points
- Healthcare providers most often diagnose diphtheria based on clinical presentation.
- Collect specimens for confirmatory testing prior to starting presumptive therapy when possible.
- Treat respiratory diphtheria with antitoxin and antibiotics.
- Antibiotics alone are usually sufficient for cutaneous diphtheria.
Diagnosis
Suspect respiratory diphtheria?
Preliminary diagnosis is usually made on the basis of clinical presentation. It's imperative to begin presumptive therapy quickly before confirmatory test results are available.
Testing begins with culturing the site where diphtheria is suspected (e.g., a pharyngeal or skin wound culture). Collect bacterial culture specimens prior to antibiotic treatment, if possible.
If C. diphtheriae are identified, further testing is needed to determine whether the strain is toxigenic. This testing is typically coordinated through the local or state public health authority and supported by CDC.
Preventing transmission
C. diphtheriae aren't thought to be contagious once a patient finishes 48 hours of antibiotic treatment. However, when C. diphtheriae are toxigenic, document bacteria elimination by obtaining two consecutive negative cultures 24 hours apart, once antibiotic therapy is completed. This is true for all types of diphtheria, including respiratory and cutaneous presentations.
Respiratory diphtheria
Maintain droplet precautions until the patient completes their antibiotic course and is culture-negative.
Cutaneous diphtheria
Contact precautions are recommended for cutaneous disease until the patient is culture-negative.
Treatment
Respiratory and cutaneous diphtheria: Only erythromycin or penicillin is recommended.
While C. diphtheriae are often sensitive to many antibiotics, in vivo data aren't available to demonstrate their effectiveness in clearing the infection.
Respiratory diphtheria: Diphtheria antitoxin (DAT) is recommended.
Cutaneous diphtheria: Antitoxin isn't typically needed.
In the United States, healthcare providers can obtain diphtheria antitoxin from CDC on request.
Management
Respiratory support and airway maintenance may be needed. Monitor cardiac and neurologic status closely due to the risk of developing myocarditis and neuritis.
Prevention
Vaccination after recovery
Diphtheria might not confer immunity. Confirm all patients recovering from diphtheria are up to date with their vaccinations. If not, administer diphtheria toxoid-containing vaccine during convalescence.
Management of close contacts
State or local health departments investigate all suspected respiratory and non-respiratory diphtheria cases to identify close contacts.
Management of close contacts should include
- Maintaining quarantine for 7 to 10 days after last exposure
- Monitoring for diphtheria during quarantine
- Obtaining cultures (nasal and throat)
- Providing prophylaxis (erythromycin or penicillin)
- Vaccinating anyone who is not up to date with diphtheria vaccines
Additional prophylaxis guidance
When there are compliance concerns, close contacts should receive a dose of intramuscular benzathine penicillin.
Additional vaccination guidance
Close contacts whose last diphtheria-containing vaccine was more than 5 years prior should receive an additional dose.