Correct Species Identification of Streptococcus Using Multi LocusSequence Analysis for Disproving Relapse of Two Episodes of InfectiveEndocarditis

When repetitive infective endocarditis episodes occur in the same patient, accurate species identification is essential for differentiating relapse and a new episode. We report a case, which has had four episodes of IE within 2 years: episode 1 due to Enterococcus faecalis, episode 2 due to Mitis group Streptococcus, Episodes 3 and 4 due to Salivarius group Streptococcus. Detailed molecular examinations using Multi Locus Sequence Analysis (MLSA) convincingly documented that the two strains from episodes 3 and 4 were different. Thus, it was not a relapse, but a new infection and, importantly, not the result of antibiotic treatment failure.