Identifying the Portal of Entry in Bacterial Endocarditis: A Quest to the Source

Background: Infective endocarditis (IE) results from bacterial seeding of the heart valves. Causative bacteria can be grouped according to the likely source such as skin, oral cavity or bowel. This allows for screening of a portal of entry (POE) to prevent recurrent IE and to identify underlying pathologies such as colonic malignancies or oral lesions. Rates of routine screening for POE are largely unknown. Methods: At our tertiary hospital, a retrospective analysis identified 86 patients over 18 months with a new diagnosis of infective endocarditis. We assessed if a POE was identified and if screening for POE was performed appropriate to the causative bacteria. Results: The POE was identified in 51 (59%) of patients. Intravenous drug use was present in 28% of identified POEs. Cutaneous infection was the most common POE (67%) followed by oral and gastrointestinal sources. Over 50% of infections with gastrointestinal and oral flora arose from an unknown POE. In 5 patients with gastrointestinal POEs identified, 2 had pre-malignant polyps and 1 had a malignant tumour. 48% of patients requiring inpatient valve surgery had an unknown POE with 4 cases of recurrent-prosthetic IE. Conclusions: In the absence of a protocol for identifying the POE in infective endocarditis, the source of infection remains unknown in a significant number of patients. Without identifying the source of the initial insult, these patients are at future risks of re-infection, which carries significant morbidity and mortality, especially in those with prosthetic heart valves. Our results highlight the need to standardise POE investigation to reduce the incidence of recurrent infective endocarditis.