Researchers from the Institut Pasteur in Paris, working with the European Diphtheria Consortium, have analyzed 363 cases of toxin-producing Corynebacterium diphtheriae infections reported across 10 European countries during 2022. Their findings were published in the New England Journal of Medicine.
Of the total cases, 77% involved cutaneous diphtheria, while respiratory diphtheria accounted for 15%. A smaller percentage—2.3%—showed both respiratory and cutaneous symptoms. The research team conducted whole-gene sequencing and tested antimicrobial susceptibility of the isolates.
Their results indicated that strains carrying the ermX gene displayed resistance to erythromycin. Strains with the pbp2m gene were found to be resistant to penicillin but remained susceptible to amoxicillin.
The study authors stated, “The distribution of each genetic cluster of C. diphtheriae isolates across multiple countries in Europe showed repeated cross-border spread. The large number of C. diphtheriae infections among migrants is a cause for concern, particularly given that antimicrobial-resistance phenotypes threaten the efficacy of first-line treatments.”
The researchers highlighted concerns about international travel contributing to disease spread and underscored that current patterns of antimicrobial resistance challenge existing treatments for diphtheria. They emphasized vaccination as a key preventive measure against this threat.
