Non-toxigenic Corynebacterium diphtheriae as a cause of bacterial endocarditis in children with congenital heart defects
Abstract number: p567
Dove M.G., Loxton R.P., Olivier E.J., Prinsloo B.
Non-toxigenic strains of C. diphtheriae have been increasingly recognised as a cause of invasive disease. Bacteraemia and endocarditis caused by these strains have been reported with increasing frequency. Other invasive diseases such as septic arthritis, splenic abscesses and mycotic cerebral aneurisms have also been described. To date at least 67 cases of non-toxigenic C. diphtheriae causing endocarditis have been reported worldwide. Most of these cases were in either native or prosthetic heart valves and in IV drug abusers.
We report on 4 cases of infective endocarditis caused by non-toxigenic C. diphtheriae in patients with underlying congenital heart defects, occurring at the Pretoria Academic Hospital over the past 7 years.
Endocarditis was confirmed by the presence of diphtheroid organisms in the blood cultures of all the patients. A final diagnosis was made on microscopy (Gram and Albert's stains), culture on blood agar and Hoyle's medium, in-house biochemical tests substantiated by API CORYNE (Biomerieux) An elek test for toxin production was performed on all isolates.
The ages of the 4 patients were between 3 and 16 years. Positive blood cultures (Bactec 9240 System) were obtained from all patients on multiple occasions. Characteristic "Chinese letter" arrangements of the bacilli were seen on both Gram and Albert's stains, as were metachromatic granules. In-house biochemical tests validated by API CORYNE confirmed all organisms to be C. diphtheriae var gravis. Elek tests in all cases indicated no toxin production. Sensitivities to a number of antibiotics (ampicillin, penicillin, erythromycin, gentamicin, piperacillin and cefuroxime) were determined by the Kirby-Bauer disc diffusion method. With the exception of penicillin and ampicillin resistance in one patient, all antibiotics tested were sensitive. Patients were treated with penicillin and gentamicin parenterally and all survived without complications.
Non-toxigenic C. diphtheriae is an infectious pathogen, and detection of coryneform bacteria in the blood can no longer be dismissed as contamination and must be investigated. Failure to recognise this pathogen can delay final diagnosis and initiation of appropriate chemotherapy. Species identification is important as mortality differs with the different biotypes. The importance of this organism as emergent pathogen should not be underestimated.
|Session name:||XXIst ISTH Congress|
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