Streptococcus anginosus (“Streptococcus milleri”)

Experimental endocarditis induction and platelet aggregation by Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius

A total of 18 'Streptococcus milleri' strains including the ATCC type strains of Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius were compared with Streptococcus oralis ATCC10557 for their ability to induce infective endocarditis in catheterized rats. Three days after intravenous injection of 10(8) colony-forming units all 8 S. anginosus strains tested produced infective vegetations and bacteremia in almost all rats whereas 5 S. constellatus strains and the S. oralis strain produced infective vegetations and bacteremia less frequently and 5 S. intermedius strains only occasionally. The vegetations infected with the S. anginosus strains harbored microbial cells in significantly higher numbers that those with the other strains. No strong correlation was found between the endocardial infectivity and platelet-aggregating capacity of these strains. The platelet-aggregating strains were members of the Lancefield groups F and G or ungroupable but not of group A or C.

Group-C beta-hemolytic streptococcal bacteremia

Group-C beta-hemolytic streptococci (GCBHS) is an uncommon cause of bacteremia. In a 5-year period, GCBHS accounted for 0.28% of positive blood cultures and 0.35% of bacteremias documented at our hospital. The incidence of GCBHS bacteremia was 0.05 episodes per 1000 admissions. We were able to analyze clinical data of 10 of the 13 patients with GCBHS bacteremias. All but one were adults with significant underlying diseases, and seven episodes were community acquired. The skin was the portal of entry in only one case. Clinical syndromes included primary bacteremia (four cases), pneumonia (two cases), endocarditis (two cases), and meningitis, intraabdominal infection, and metastatic suppurative pericarditis (one episode each). Of 13 isolates, 12 were identified to species level: six, Streptococcus equisimilis; three S. equi; two S. dysgalactiae; and one S. zooepidemicus. Resistance to penicillin was detected in one isolate and none of our isolates displayed penicillin tolerance, Four patients died (40%) despite appropriate antimicrobial therapy.