Characteristics of Streptococcus bovis endocarditis and its differences with Streptococcus viridans endocarditis

The purpose of this study was to evaluate the characteristics of infective endocarditis (IE) caused by S. bovis and compare them to those caused by streptococci of the viridans group (SVG). A prospective study was undertaken considering 55 consecutive cases of IE due to S. bovis and 41 to SVG over 18 years. The study was divided into two periods ( 1988-1996 and 1997-2005). S. bovis caused 24% of the IE in our centre and constituted the main aetiology for this disease, showing an increase of 358% during the second period studied. Biotype I was responsible for 94.5% of cases and there was a high degree of association with colon tumours (53%). Over the period of the study, 107 patients admitted to our hospital had bacteraemia caused by S. bovis and 310 patients had bacteraemia caused by SVG. In the first group, 55 (51%) were endocarditis cases, but only 41 (13%) of the patients with SVG bacteraemia had endocarditis (p< 0.0001). The distinguishing features of endocarditis caused by S. bovis in comparison with those caused by SGV were: a greater increase in cases during the 2nd period studied ( from 12 to 43 vs. from 19 to 22, p< 0.01), a higher percentage of males (93% vs. 71%, p< 0.004), patients significantly older ( median age 66 vs. 58.5, p< 0.004), less predisposing cardiopathy (42% vs. 76%, p< 0.0009), more bivalvular involvement ( 42% vs. 22%, p< 0.04), more spondylitis (9% vs. 0%, p< 0.04), a higher association with colonic tumours ( 53% vs. 5%, p< 0.0001), and a higher percentage of antibiotic resistance: erythromycin 66% vs. 19%, p< 0.0001; clindamycin 67% vs. 11%, p< 0.0001; cotrimoxazole 77% vs. 30.5%, p< 0.0001, respectively. IE due to S. bovis is an emergent disease in our environment, presenting different characteristics to those produced by SVG.