IDENTIFICATION OF A NOVEL INSERTION ELEMENT, IS1548 IN GROUP-B STREPTOCOCCI, PREDOMINANTLY IN STRAINS CAUSING ENDOCARDITIS

Hyaluronidase has been postulated to be a virulence factor in group B streptococci (GBS). No hyaluronidase activity was found in 15 of 50 GB S isolates from adults studied. Most of these hyaluronidase-negative s trains belonged to serotype III. In strains lacking hyaluronidase acti vity, an insertion of 1317 nucleotides was found in the hyaluronidase gene. The fragment was cloned and sequenced and found to have characte ristics of a novel insertion sequence, designated IS1548. As well as i n GBS serotype III, this sequence was found in 3 of 6 serotype II isol ates and in all 10 group A streptococcal strains (GAS) tested. Homolog ies were found with repeated sequences in Streptococcus pneumoniae and with H repeats in Escherichia coli. All GBS strains harboring IS1548 and some GAS strains had one copy of IS1548 located downstream of the C5a peptidase gene. IS1548 was present in 9 of 13 GBS isolates from bl ood in endocarditis patients and in 3 of 22 vaginally colonizing strai ns.