Staphylococcus aureus bacteraemia: evaluation of the role of transoesophageal echocardiography in identifying clinically unsuspected endocarditis

Abstract

Staphylococcus aureus bacteraemia (SAB) is an important cause of community and nosocomial sepsis, with a significant mortality rate. Infective endocarditis (IE) is a serious complication, occurring in up to 25 % of cases. Transoesophageal echocardiography (TOE) significantly improves the sensitivity of diagnosis. We compared the sensitivity and specificity of clinical evaluation alone in diagnosing IE. We evaluated all adult patients with SAB at our centre from 1998 to 2006 in order to determine what proportion of clinically unsuspected cases were diagnosed with IE on TOE. IE was defined according to modified Duke criteria. The median age of the patients was 68 years, 77 % were male and the majority of cases did not have a known pre-existing condition. Twenty-one percent were methicillin-resistant Staphylococcus aureus (MRSA). Intravascular device was the most common cause of bacteraemia. TOE was performed in 144 (100 %) of the cases. IE was suspected clinically in 15 % of cases, and the overall prevalence of possible or definite IE on TOE-inclusive Duke criteria was 29 % (n = 41). Following TOE, 22 (15 %) cases were reclassified as either possible or definite endocarditis. TOE detected a vegetation in 37 (90 %) of the 41 cases of IE. Nineteen (46 %) were not suspected clinically by Duke criteria. Sensitivity improved in the presence of pre-existing valve lesion or community acquisition. The overall in-hospital mortality was 10 %. There is a high incidence of endocarditis in SAB and a large percentage of cases are not evident on clinical grounds. TOE evaluation is indicated for all medically suitable adult patients with SAB in order to improve the detection of endocarditis.