Pathogenesis of Endocarditis – Bacteraemia of Oral Origin

Bacteraemia is defined as the presence of bacteria in the blood. A feature that is unique to the oral bacterial biofilm, particularly the subgingival plaque biofilm, is its close proximity to a highly vascularised milieu. Any disruption of the natural integrity between the biofilm and the subgingival epithelium, which is at most about 10 cell layers thick, could lead to a bacteraemic state (Parahitiyawa et al., 2009). For several decades, the haematogenous spread of bacteria from the oral cavity has been considered a decisive factor in the pathogenesis of 10% to 15% of cases of infective endocarditis (IE); certain dental procedures may therefore carry a significant risk (Carmona et al., 2002). However, this statement has come under question, its detractors argue that not all patients with heart valves infected by bacteria that typically colonize ecological niches of the oral cavity have undergone dental procedures. Furthermore, there is as yet little evidence of genetic similarity between bacteria isolated from the heart valves, the bloodstream, and the oral cavity of patients with IE (Pallasch, 2003; Seymour et al., 2000).