Background: Invasive infections caused by C. diphtheriae were rarely reported.
Methods: We report the 2 patients with C. diphtheriae endocarditis in King Chulalongkorn Memorial hospital
Results: Case 1: a 60-year-old woman with mitral and aortic prosthetic valves presented with fever and myalgia for 6 hours. Examination revealed irregular heart rate, positive heart valve clicks. Cerebrospinal fluid showed mononuclear cells 2 cells/µL, glucose of 104 mg/dL, protein of 20 mg/dL. The initial diagnosis was septicemia. Fifteen hours after incubation, 2 blood culture specimens grew C. diphtheriae with the analytical profile index (API) indicating C. diphtheriae subsp. mitis strain belfanti of 96% identity. The diphtheria toxin was negative by Eleks test. Transthoracic echocardiogram (TTE) showed no vegetation, but with some limitations due to prosthesis-associated artifacts. Eight days after hospitalization, she had retroperitoneal hemorrhage due to ruptured aneurysm from abnormal vessels as demonstrated by CT (Figure 1). The bleeding was stopped by the embolization. The final diagnosis was probable C. diphtheriae prosthetic valve endocarditis, and the treatment was penicillin G sodium (PGS). The patient was discharged 4 weeks after hospitalization.
Case 2: A 16-year-old man presented with fever for 3 days and dyspnea for 4 hours. Examination revealed engorged jugular veins, S3 gallop, and fine crepitation of both lungs. Fourteen hours after incubation, 2 blood culture specimens grew C. diphtheriae with the API indicating C. diphtheriae subsp. mitis strain belfanti of 95.9% identity. The diphtheria toxin was negative. TTE showed a 8-mm oscillating mass at anterior mitral valve leaflet (Figure 2). The final diagnosis was C. diphtheriae endocarditis. He underwent mitral valve replacement because of refractory heart failure and PGS of 24 million units/day was given. He was discharged 8 weeks after hospitalization.
Conclusion: There should be a high index of suspicion of C. diphtheriae endocarditis in patients at high risk such as non-vaccinated or elderly individuals who presented with primary bacteremia.
Figure 1. Large retroperitoneal hematoma in accompanying with feeding vessel (an arrow).
Figure 2. A 8-mm oscillating mass (an arrow) at anterior mitral valve leaflet
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