Initial Treatment for Diphtheroid Infections

Critical First Step: Distinguish True Diphtheria from Other Diphtheroids

The American College of Physicians recommends initiating a 14-day course of oral erythromycin (40 mg/kg/day in children; 1g/day in adults) immediately, combined with prompt administration of equine diphtheria antitoxin after sensitivity testing for true diphtheria caused by toxigenic Corynebacterium diphtheriae 1
The Centers for Disease Control and Prevention suggests that diphtheria antitoxin (equine) should be administered after sensitivity testing, with a dosing of 5,000-10,000 units IM at a site different from toxoid injection, due to a 7% risk of immediate hypersensitivity reactions and 5% risk of serum sickness 2

The American Academy of Pediatrics recommends starting antibiotic therapy immediately with either erythromycin 40 mg/kg/day (children) or 1g/day (adults) orally for 14 days, or benzathine penicillin IM as a single dose of 600,000 units (<6 years) or 1,200,000 units (≥6 years) 1
The Infectious Diseases Society of America advises obtaining follow-up cultures after completing antimicrobial therapy, and if cultures remain positive, administering an additional 10-day course of oral erythromycin 2

The World Health Organization recommends that if follow-up cultures remain positive after completing antimicrobial therapy, an additional 10-day course of oral erythromycin should be administered 1, 2

The Centers for Disease Control and Prevention recommends that all close contacts require prophylaxis regardless of vaccination status, with antimicrobial prophylaxis using erythromycin orally for 7-10 days (40 mg/kg/day in children; 1g/day in adults) 1

The International Working Group on the Diabetic Foot suggests that when diphtheroids are isolated from diabetic foot infections with clinical evidence of infection, mild infections should be treated by targeting gram-positive pathogens empirically and adjusting based on culture results 3
The American Diabetes Association recommends that for moderate-severe infections, broader coverage should be used initially, then narrowed based on susceptibilities, and that high-quality tissue samples (not superficial swabs) are essential to determine the pathogenic versus colonizing role of Corynebacterium species 3