What is the recommended medication for treating diphtheroids (diphtheria)?

Treatment of Diphtheria

Erythromycin or penicillin are the recommended medications for treating diphtheria, with erythromycin being the first-line treatment in most cases. 1, 2

Primary Treatment Approach

Antimicrobial Therapy

• For active diphtheria infection, a 14-day course of oral erythromycin (children: 40 mg/kg/day; adults: 1g/day) is recommended to eliminate the organism and prevent toxin production 1
• Alternative treatment is benzathine penicillin administered as an intramuscular injection (600,000 units for persons less than 6 years old and 1,200,000 units for those greater than or equal to 6 years old) 1
• Erythromycin may be slightly more effective at eliminating the organism, but penicillin has the advantage of single-dose administration which improves compliance 1
• Treatment must be continued for the full duration to minimize treatment failure and prevent relapse 3

Antitoxin Administration

• Diphtheria antitoxin (equine) must be administered promptly in conjunction with antibiotics for patients with clinical diphtheria 1
• Antitoxin neutralizes circulating toxin but cannot reverse damage already done by the toxin 1
• Sensitivity testing should be performed before administering equine antitoxin due to risk of allergic reactions 1

Treatment Considerations

Timing of Treatment

• Early administration of antimicrobial therapy is critical - treatment initiated during the catarrhal stage or early paroxysmal stage has better outcomes 1, 4
• Delay in treatment increases risk of systemic complications including myocarditis and neuropathy 5

Monitoring and Follow-up

• Follow-up cultures should be obtained after completion of antimicrobial therapy to ensure eradication of the organism 3
• Cultures should be taken at least 2 weeks after completion of therapy, as shorter follow-up periods may miss relapses 3
• If cultures remain positive after treatment, an additional 10-day course of erythromycin should be administered 1

Resistance Considerations

• Some strains of C. diphtheriae have shown resistance to erythromycin (up to 27% in some studies) 6
• In areas with known erythromycin resistance, penicillin may be preferred as first-line therapy 6

Management of Contacts

• All close contacts of diphtheria patients should receive antimicrobial prophylaxis regardless of vaccination status 1
• Prophylaxis options include:
  • Erythromycin orally for 7-10 days (children: 40 mg/kg/day; adults: 1g/day) 1
  • Benzathine penicillin IM single dose (600,000 units for persons <6 years; 1,200,000 units for those ≥6 years) 1
• Cultures should be obtained from all close contacts before starting prophylaxis 1
• Unvaccinated or incompletely vaccinated contacts should receive diphtheria toxoid-containing vaccine 1

Special Considerations

Cutaneous Diphtheria

• For toxigenic strains causing cutaneous diphtheria, the same antimicrobial regimen is recommended as for respiratory diphtheria 1
• For non-toxigenic cutaneous infections, routine investigation or prophylaxis of contacts is not necessary 1

Carriers

• Carriers of C. diphtheriae should receive the same antimicrobial treatment as active cases 3
• Studies show that short courses (6 days) of erythromycin result in high relapse rates (21%) 3
• The full 14-day course is essential to prevent carrier relapse 3

Pitfalls and Caveats

• Relying solely on antimicrobial therapy without antitoxin administration can lead to treatment failure in clinical diphtheria 1, 5
• Short courses of antibiotics (<14 days) have high relapse rates 3
• Failure to follow up with post-treatment cultures may miss persistent carriers 3
• In areas with erythromycin resistance, using it as first-line therapy may be ineffective 6
• Equine antitoxin carries risk of allergic reactions (7% immediate hypersensitivity, 5% serum sickness) and requires sensitivity testing 1