Non-toxigenic Corynebacterium diphtheriae endocarditis: A cluster of five cases

Tamsin Lovelock; Mignon du Plessis; Clinton van der Westhuizen; Jacques T Janson; Charlene Lawrence; Arifa Parker; Alfonso Pecoraro; Hans Prozesky; Anne von Gottberg; Jantjie Taljaard

doi:10.4102/sajid.v39i1.539

Non-toxigenic Corynebacterium diphtheriae endocarditis: A cluster of five cases

S Afr J Infect Dis. 2024 Feb 21;39(1):539. doi: 10.4102/sajid.v39i1.539. eCollection 2024.

Authors

Affiliations

¹ Division of Infectious Diseases, Department of Medicine, Faculty of Health Sciences, Stellenbosch University and Tygerberg Hospital, Cape Town, South Africa.
² Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases, Johannesburg, South Africa.
³ School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
⁴ Department of Medical Microbiology, Tygerberg Hospital, National Health Laboratory Service, Cape Town, South Africa.
⁵ Division of Medical Microbiology and Immunology, Department of Pathology, Tygerberg Hospital/Stellenbosch University, Cape Town, South Africa.
⁶ Division of Cardiothoracic Surgery, Department of Surgery, Tygerberg Hospital/Stellenbosch University, Cape Town, South Africa.
⁷ Western Cape Government, Department of Health and Wellness, Emergency and Clinical Services Support, Service Priorities Coordination, Communicable Disease Control and Outbreak Response, Cape Town, South Africa.
⁸ Division of Cardiology, Department of Medicine, Stellenbosch University and Tygerberg Hospital, Cape Town, South Africa.

Abstract

Background: Classical toxin-mediated respiratory diphtheria has become less common because of widespread effective vaccination globally but invasive disease as a result of non-toxigenic strains of Corynebacterium diphtheriae is not prevented by vaccination and may result in severe disease, including infective endocarditis (IE).

Objectives: To describe the outbreak and subsequent investigation of a cluster of five cases of non-toxigenic C. diphtheriae endocarditis.

Method: A retrospective observational case series of five cases of non-toxigenic C. diphtheriae endocarditis identified in the rural West Coast district of the Western Cape province of South Africa between May 2021 and June 2021.

Results: Non-toxigenic C. diphtheriae IE had an aggressive clinical course with high mortality in this cohort. Only one of five patients survived to hospital discharge. The surviving patient received a prompt diagnosis with early surgical intervention but still had a complicated clinical course. Notably, only one case had a pre-existing risk factor for IE, namely a prosthetic valve. Whole genome sequencing of clinical isolates confirmed that all isolates were of the same novel sequence type of non-toxigenic C. diphtheriae but despite a thorough investigation no epidemiological link was ever found between the cases.

Conclusion: Non-toxigenic strains of C. diphtheriae are less well known but may be highly virulent and cause severe invasive disease.

Contribution: This is the largest cluster of non-toxigenic C. diphtheriae IE ever described in South Africa and expands the body of literature on this unusual but possibly emerging infection.

Keywords: infective endocarditis; non-toxigenic Corynebacterium diphtheriae; outbreak.

Grants and funding

Funding information This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.