Structure of scpB-lmb intergenic Region as Criterion for Additional Classification of Human and Bovine Group B Streptococci
Acta Veterinaria Brno
Dmitriev A., A. D. Shen, ª. Tkáãiková, I. Mikula, Y. H. Yang: Structure of scpBlmb Intergenic Region as Criterion for Additional Classification of Human and Bovine Group B streptococci. Acta vet. Brno 2004, 73: 215-220. The relative location of scpB and lmb genes in group B streptococcal (GBS) strains was studied. These genes were found in all the strains isolated from human and only in 9% of strains isolated from dairy cows. The scpB gene was located upstream of the lmb gene, however, three
... , however, three different structures of scpB-lmb intergenic region were identified. These genes could be separated by the 164 bp spacer region (type 1), by this spacer region with insertion sequence IS1548 (type 2) or by this spacer region with intron GBSi1 (type 3). The presence of different insertion sequences (IS861, IS1548, ISSa4 and IS1381) was compared with serological types of GBS strains and the types of scpB-lmb intergenic region structure. As a result, 10 different genetic variants were identified in GBS. The genetic variants No. 1 -No. 9 were found in human strains while the variant No.10 was found only in bovine strains. The mutually exclusive presence of insertion sequences IS1548, ISSa4 and the type 3 structure of scpB-lmb intergenic region was demonstrated. The structure of scpB-lmb intergenic region was found to be useful criterion for additional classification of GBS strains. Streptococcus agalactiae, classification, insertion sequence, intron Streptococcus agalactiae (group B streptococcus, GBS) is an important human and animal pathogen that causes invasive infections in neonates as well as mastitis of the dairy cows (Regan at al. 1996; Keefe 1997) . Recently the numerous genes encoding for the potential virulence factors were identified in GBS (Jones et al. 2000). In particular, the genes scpB and lmb encoding for C5a peptidase and laminin binding protein, respectively, were considered to be involved in GBS virulence (Chmouryguina et al. 1996; Spellerberg et al. 1999) . Previously we analyzed a large collection of GBS strains and found that the genes scpB and lmb were present in all the strains of human origin. At the same time these genes were found only in a few strains of bovine origin (Dmitriev et al. 2002a; Dmitriev et al. 2002b) . After pulsed field gel electrophoresis we found that the genes scpB and lmb were closely located in GBS genome (Dmitriev et al. 2002a; Dmitriev et al. 2002b) . The goal of the present study was to further investigate the precise relative location of scpB and lmb genes in GBS strains. Materials and Methods Bacterial strains A total of 169 epidemiologically unrelated GBS strains were analyzed. Among them, 79 strains were isolated from the pregnant women in Beijing and Guangzhou (P. R. China) in 1996-2000, 12 strains were isolated from pregnant women in Saint-Petersburg (Russia) in 1989-1995 and 78 strains were isolated from the dairy cows in different regions of Eastern Slovakia in 1999-2002. Bacteria were grown either in Todd-Hewitt broth or on 1.5% sheep blood agar at 37 °C overnight. After serological typing it was found that most of bovine strains were nontypeable. On the contrary, the human strains belonged to different serological types (Ia, Ia/c, Ib/c, II, II/c, II/R, III, III/R, V) and only 3 of 91 human strains (3.3%) were non-typeable (Table 2) .