Case Report Usefulness of 16S rDNA sequencing for the diagnosis of infective endocarditis caused by Corynebacterium diphtheriae Padmaja Pathipati, 1 Thangam Menon, 2 Naveen Kumar, 2 Thara Francis, 1 Prem Sekar 3 and Kotturathu Mammen Cherian 4 Correspondence Thangam Menon thangam56@gmail.com Received 2 June 2011 Accepted 20 April 2012 1 Department of Microbiology, Frontier Lifeline Hospital, Mogappair, Chennai, India 2 Department of Microbiology, University of Madras, Dr ALM Post Graduate Institute of Basic Medical Sciences, Taramani, Chennai, India 3 Department of Paediatric Cardiology, Frontier Lifeline Hospital, Mogappair, Chennai, India 4 Department of Cardiothoracic Surgery, Frontier Lifeline Hospital, Mogappair, Chennai, India We report a rare case of infective endocarditis caused by Corynebacterium diphtheriae in an 8- year-old boy, 2 years after a right ventricular outflow tract reconstruction with a bovine Contegra valved conduit. The patient recovered well after an RV–PA conduit enblock explantation and replacement with an aortic homograft with antibiotic treatment. All bacteriological cultures of excised tissue and blood were negative. The aetiological agent was identified as C. diphtheriae subsp. gravis by 16s rDNA sequencing. Introduction Infective endocarditis (IE) is a severe disease and identification of the aetiological agent is necessary to facilitate rapid and effective therapy. Conventional meth- ods used in most clinical laboratories to diagnose IE include detection of micro-organisms in blood cultures, excised cardiac valves or vegetations. These methods often fail because of previous antimicrobial therapy or the involvement of fastidious, slow-growing or non-cultivable micro-organisms. To overcome this, culture independent molecular techniques based on the amplification and direct sequencing of ribosomal sequences have been developed (Breitkopf et al., 2005). We describe the clinical usefulness of broad range 16S rDNA amplification in the identification of Corynebacterium diphtheriae from an explanted Contegra bovine jugular vein conduit. Case report An 8-year-old male born to non-consanguineous parents was referred to our hospital on 30 December 2010 with a clinical diagnosis of infective endocarditis (IE) and right ventricular outflow tract obstruction. He had a history of congenital heart disease and in November 2008, underwent intra-cardiac repair with a valved right ventricle–pulmonary artery (RV–PA) 18 mm Contegra conduit for Tetralogy of Fallot in a city hospital. The patient was asymptomatic until November 2010, when he developed intermittent fever with facial oedema and severe anaemia. He was treated for suspected endocarditis in a local hospital with intravenous penicillin and gentamicin for 10 days, although blood cultures were negative. Subsequently, he was transferred to another hospital where he was treated with penicillin, amikacin and piperacillin–tazobactam. Since he had symp- toms of persistent infection and fever continued in spite of medical management, he was referred to our hospital. On physical examination, the child appeared thin, pale and generally unwell and was febrile. Blood pressure was 100/ 60 mmHg, heart rate was 118 min 21 and auscultation revealed an ejection systolic murmur of grade 4/6. He had mild pallor and oedema but no cyanosis or icterus. His parents reported that he had been given all the childhood immunizations as scheduled. Chest X-ray showed levocar- dia, cardiomegaly with enlarged right atrium and normal lung vascularity. Laboratory studies revealed an erythrocyte sedimentation rate of 50 mm h 21 ; haemoglobin of 9.6 g dl 21 ; total white blood cell count of 9.8610 9 l –1 , with a differential count of 85 % neutrophils, 12 % lymphocytes and 0.3 % eosinophils; and C-reactive protein of 51.30 mg l –1 . Kidney and liver function tests were normal. Two sets of blood cultures, which were processed using the Bact Alert 3D system (bioMe ´rieux), showed no growth. Abbreviations: IE, infective endocarditis; RV–PA, right ventricle– pulmonary artery. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of the Corynebacterium diphtheriae isolate obtained in this study is JQ396647. Journal of Medical Microbiology (2012), 61, 1159–1161 DOI 10.1099/jmm.0.034710-0 034710 G 2012 SGM Printed in Great Britain 1159