Corynebacterium diphtheriae Infections, South Africa, 2015-2023

Abstract

We reviewed Corynebacterium spp. infection cases reported in South Africa during 2015-2023. We analyzed 84 isolates from 83 patients with C. diphtheriae, as well as 1 C. belfantii and 3 C. ulcerans isolates. Among C. diphtheriae cases, we observed respiratory diphtheria (26/83 patients [31%]), endocarditis (14/83 [17%]), cutaneous diphtheria (22/83 [27%]), nonspecific respiratory illnesses (5/83 [6%]), and asymptomatic carriage (16/83 [19%]). The median patient age was 19 (range 0-88) years. Diphtheria-tetanus-pertussis vaccination was incomplete for 26% (5/19) or unknown for 68% (13/19) of children 0-9 years of age. C. diphtheriae was intermediately resistant to penicillin (82/84 [98%] isolates; MIC₉₀ 0.5 μg/mL) but susceptible to erythromycin (83/84 [99%] isolates; MIC₉₀ 0.25 μg/mL). Eighteen unique sequence types were identified, corroborating C. diphtheriae heterogeneity. Toxin-producing strains were detected among cutaneous and respiratory diphtheria cases, indicating all forms of disease require monitoring and prompt public health action to curb transmission.

Keywords: 2015–2023. Emerg Infect Dis. 2025 Mar [date cited]. https://doi.org/10.3201/eid3103.241211; Corynebacterium diphtheriae; DTP vaccine; Duma N; Lawrence C; Lovelock T; Mikhari R; South Africa; Suggested citation for this article: du Plessis M; antimicrobial resistance; bacteria; cutaneous diphtheria; de Gouveia L; diphtheria; diphtheria toxin; et al. Corynebacterium diphtheriae infections; genome; infective endocarditis; molecular epidemiology; tox gene.

Figure 1

Corynebacterium diphtheriae infections according to year and clinical illness category, South Africa, 2015–2023. Total number of cases was 83.

Figure 2

Phylogenetic analysis of Corynebacterium diphtheriae isolates, South Africa, 2015–2023. Total number of isolates was 84 from 83 patients. Isolate identification numbers are listed on the right side of the colored bars. Colored columns indicate presence/absence of the tox gene, sequence type, sublineage, location of isolate, year isolate was collected, and clinical infection type. Neighbor-joining tree was generated by using the core genome multilocus sequence typing scheme in the Insitut Pasteur Bacterial Isolate Genome Sequence C. diphtheriae database (https://bigsdb.pasteur.fr/diphtheria). Tree was visualized by using iTOL (https://itol.embl.de) and rooted by using a tox gene–negative C. diphtheriae genome (no. 1597 at top) isolated from South Africa circa 1980 (clinical isolate with no available clinical or demographic data). Scale bar indicates nucleotide substitutions per site. ST, sequence type.