Copyright ©ERS Journals Ltd 1998 European Respiratory Journal

The group Streptococcus milleri (SM) includes several species of pathogenic streptococci associated with pyo-genic infections. In 1956 O. Guthof was the first to use the name SM when referring to nonhaemolytic species of streptococci found in the oral cavity [1]. WHILEY and co-workers [2, 3], through phenotypic and deoxyribonucleic acid (DNA)-DNA hybridization studies, affirmed the ex-istence of at least three well-differentiated species: S. con-stellatus, S. intermedius and S. anginosus. Many authors prefer to continue using the term SM for the three species for two reasons: firstly, because the term is useful to the clinician, since it warns of the presence of a suppurative process [4, 5] and secondly, because the three species appear to be equally represented as a cause of thoracic in-fection [6, 7]