Virulence of beta-hemolytic streptococci in infective endocarditis

Background Streptococci involved in infective endocarditis (IE) primarily comprise alpha- or non-hemolytic streptococci (ANHS). Moreover, beta-hemolytic streptococci (BHS) can be involved, and guidelines recommend the addition of gentamicin for the first 2 weeks of treatment and the consideration of early surgery in such cases. This study compared the morbidity and mortality associated with IE depending on the microorganisms involved (BHS, ANHS, staphylococci, and enterococci). Methods We conducted a retrospective observational study between 2012 and 2017 in a single hospital in France. The endpoints were overall in-hospital mortality, 1-year mortality and the occurrence of complications. Results We analyzed 316 episodes of definite IE including 150 (38%), 96 (25%), 46 (12%), and 24 cases (6%) of staphylococcal, ANHS, enterococcal, and BHS IE, respectively. In-hospital mortality was significantly higher in the staphylococcal ( n = 40; 26.7%) and BHS groups ( n = 6; 25.0%) than in the ANHS ( n = 9; 9.4%) and enterococcal groups ( n = 5; 10.9%) (all p < 0.01). The rates of septic shock and cerebral emboli were also higher in the BHS group than in the ANHS group [ n = 7 (29.2%) vs. n = 3 (3.1%), p < 0.001; n = 7 (29.2%) vs. n = 12 (12.5%); p = 0.05, respectively]. Conclusion This study confirmed that BHS IE has a more severe prognosis than ANHS IE. The virulence of BHS may be similar to that of staphylococci, justifying increased monitoring of these patients and more ‘aggressive’ treatments such as early surgery.