The Resurgence of Corynebacterium Diphtheriae: A Rare Case of Infective Endocarditis

Abstract

orynebacterium diphtheriae is well known as an agent of localized respiratory tract disease potentially complicated by systemic effects of exotoxin. The non-toxigenic strains can produce atypical manifestations of the disease as they are able to cause diseases such as mild diphtheria-like pharyngitis, cutaneous infections, septic arthritis, abscesses, septicemia, and infective endocarditis (IE) [1]. IE is a grave disease with a high incidence of complications and adverse events. IE caused due to the non-toxigenic strain of C. diphtheriae is uncommon. However, there have been increasing numbers of reports of IE being caused by this organism [2]. The current vaccine against diphtheria contains the toxoid, so it protects only against the toxigenicity but not the invasiveness of C. diphtheriae. 1 Most of the patients with C. diphtheria endocarditis have underlying cardiac diseases, especially prosthetic heart valves [3]. Pathogenic mechanisms of non-toxigenic C. diphtheriae is not well known, and a possible mechanism may be related to an increased ability to adhere to vascular endothelium. It is a universally fatal disease if left untreated with nearly 100% mortality. CASE REPORT A 34-year-old prosthetic valve in situ male patient who underwent double valve replacement surgery in 2005 presented to our hospital with a 1-week history of high-grade fever with rigor and chills. He woke up 1 day noticing that the entire visual field (both eyes) was obscured. This prompted him to come to the emergency department. No other non-visual neurologic symptoms were present. He was a chronic alcoholic and was on oral anticoagulants. On general examination, he was conscious and alert. His temperature was 100.5°F, blood pressure 140/80 mmHg, and pulse rate 80/min. Ophthalmic examination revealed only light perception with both eyes and apparently normal fundus. Investigations revealed that the total leukocyte count was elevated with neutrophil predominance, and erythrocyte sedimentation rate was also elevated. To rule out the acute cerebrovascular accident, plain axial computed tomogram head was done, which could not detect any intracranial pathology. Echocardiography showed normally functioning valves and small particles in the left ventricular outflow tract and the left ventricle. Suspecting prosthetic valve endocarditis (PVE) for the patient, three blood culture samples were taken and sent to our laboratory. Two samples were taken on the 2 nd day of admission and the third sample on the following day after starting the empirical antibiotics. The patient's vision got restored on the 2 nd day of admission to the hospital without any interventions. The blood culture samples were incubated in an automated BacT/ALERT (bioMerieux) blood culture system. After 24 h of incubation, the two samples, which were taken on the 2 nd day, flagged positive and Gram staining showed Gram-positive bacilli ABSTRACT Corynebacterium species or "diphtheroids" are often considered as non-pathogenic components of the normal skin flora when isolated from blo...