Corynebacterium diphtheriae endocarditis: a case series and review of the treatment approach

Infective endocarditis due to non-toxigenic Corynebacterium diphtheriae is uncommon; we report 10 cases occurring over a 14-year period in Auckland, New Zealand and review the approach for treatment.

Eight of the 10 patients had known prosthetic valves or homografts in situ. Three patients required surgical intervention for infective endocarditis. Seven patients were treated with a combination of β-lactam and aminoglycoside, and one each was treated with a combination of vancomycin and an aminoglycoside, a β-lactam alone, and vancomycin alone. All patients survived and none relapsed.

The antibiotic treatment of 46 previously reported cases was reviewed; patients treated with a β-lactam and aminoglycoside (n=25), and without the addition of an aminoglycoside (n=11) were compared. The differences in length of treatment within each group make the comparison of outcome (mortality, need for surgical intervention, disease and treatment complications) difficult. However, regardless of the length of treatment, there was no difference in mortality or need for surgical intervention between the two groups in the currently published cases.

Current evidence suggests that endocarditis of either native or prosthetic valves, caused by penicillin-susceptible C. diphtheriae, demonstrates a favorable outcome when treated with either a β-lactam alone or in combination with an aminoglycoside. Patient-specific factors will determine which approach is more appropriate for each individual patient.