An Ongoing Diphtheria Epidemic in Guinea: Epidemiological and Microbiological Study from 2023 to 2025

Abstract

Objectives: This study describes the epidemiological and microbiological characteristics of Corynebacterium species cases between 2023 and 2025, to guide surveillance, prevention, and management. Study type: A descriptive cross-sectional study was conducted in six affected health regions. Study location and duration: All oropharyngeal or nasopharyngeal swabs meeting WHO definitions of suspected cases were centralized at the bacteriology laboratory of the National Institute of Public Health between 2023 and 2025 Methods: Bacterial identification was performed by culture on selective media (potassium tellurite agar 3.5% and Colombian agar with 5% sheep blood) and using the Corne API, and antibiotic susceptibility testing (using disk diffusion method on Mueller-Hinton agar enriched with horse blood) was interpreted according to CA-SFM/EUCAST 2023 standards. Results: Of 997 samples received, 914 were included. The median age of the patients was 7 years (IQR: 3–15 years), with a predominance of children aged 0–4 years (33.9%). The Kankan region accounted for 68.4% of reported cases. Culture was positive in 17.9% of cases (n = 164). Corynebacterium diphtheriae biovar mitis was the predominant strain (80.5%), followed by C. pseudodiphtheriticum (12.8%) and C. diphtheriae biovar gravis (6.1%). The C. diphtheriae strains showed complete susceptibility to erythromycin but high resistance to β-lactams and tetracyclines. Only one death was reported (case fatality rate of 0.1%). Conclusion: The diphtheria epidemic in Guinea is characterized by persistent transmission, primarily affecting young children, with a high geographic concentration. The results support the use of macrolides as first-line therapy, the restriction of tetracyclines and cotrimoxazole, and highlight the need to strengthen childhood vaccination and microbiological surveillance.