Prophagic DNA Fragments in Streptococcus agalactiae Strains and Association with Neonatal Meningitis

Abstract

We identified-by randomly amplified polymorphic DNA (RAPD) analysis at the population level followed by DNA differential display, cloning, and sequencing-three prophage DNA fragments (F5, F7, and F10) in Streptococcus agalactiae that displayed significant sequence similarity to the DNA of S. agalactiae and Streptococcus pyogenes. The F5 sequence aligned with a prophagic gene encoding the large subunit of a terminase, F7 aligned with a phage-associated cell wall hydrolase and a phage-associated lysin, and F10 aligned with a transcriptional regulator (ArpU family) and a phage-associated endonuclease. We first determined the prevalence of F5, F7, and F10 by PCR in a collection of 109 strains isolated in the 1980s and divided into two populations: one with a high risk of causing meningitis (HR group) and the other with a lower risk of causing meningitis (LR group). These fragments were significantly more prevalent in the HR group than in the LR group (P < 0.001). Our findings suggest that lysogeny has increased the ability of some S. agalactiae strains to invade the neonatal brain endothelium. We then determined the prevalence of F5, F7, and F10 by PCR in a collection of 40 strains recently isolated from neonatal meningitis cases for comparison with the cerebrospinal fluid (CSF) strains isolated in the 1980s. The prevalence of the three prophage DNA fragments was similar in these two populations isolated 15 years apart. We suggest that the prophage DNA fragments identified have remained stable in many CSF S. agalactiae strains, possibly due to their importance in virulence or fitness.Streptococcus agalactiae, a bacterial pathogen frequently carried in the normal fecal and/or vaginal flora, is a leading cause of severe bacterial infections in neonates (33). The characterization of S. agalactiae strains, initially by multilocus enzyme electrophoresis (MLEE) (26,29) and then by multilocus sequence typing (16) and various other methods (5, 39), has revealed the existence of two strongly differentiated lineages in the species. The first is a homogeneous lineage composed of serotype III strains, and the second is a genetically diverse lineage composed of isolates from all capsular serotypes, including serotype III.

Genetic diversity of Streptococcus agalactiae strains and density of vaginal carriage

“…As previously shown, strains able to invade the central nervous system of neonates frequently carry certain genetic markers at significant levels. Two of these markers are mobile genetic elements [the GBSi1 group II intron downstream from the C5a-peptidase scpB gene (Rolland et al, 1999) and IS1548 in the hylB gene, which encodes a hyaluronate lyase (Granlund et al, 2001)] and three are prophagic DNA fragments (van der Mee-Marquet et al, 2006). PCR was used to test for the presence of these genetic markers as previously described (Bidet et al, 2003;Rolland et al, 1999;van der Mee-Marquet et al, 2006) (see Supplementary Table S1 for primers).…”

“…In addition, genetic markers have been associated with virulent phylogenetic subgroups of strains. These are the insertion sequence IS1548 in the hylB gene (Granlund et al, 2001), a group II intron GBSi1 that is located downstream from the C5a-peptidase gene scpB (Rolland et al, 1999) and the presence of particular prophage DNA fragments in the S. agalactiae genome (van der Mee-Marquet et al, 2006).…”

The Threat of Aerobic Vaginitis to Pregnancy and Neonatal Morbidity

“…GBS exists as normal microbiota in the female genital tract and anal areas of healthy adults [43][44][45][46] , with an estimated one out of three women being a carrier of GBS. The gastrointestinal tract serves as the natural reservoir for GBS and is expected to be the source of vaginal colonization 23,43 .…”

Clinical Features of Group B Streptococcus Prosthetic Joint Infections and Molecular Characterization of Isolates

“…The presence of GBS genetic markers previously reported in GBS neonatal central nervous system (CNS) infections was determined by PCR (5,8,15). The markers analyzed were mobile genetic elements, including the GBSi1 group II intron downstream of the C5a-peptidase gene scpB and IS1548 associated with the hylB gene, and prophage DNA fragments F5, F7, and F10.…”

“…The markers analyzed were mobile genetic elements, including the GBSi1 group II intron downstream of the C5a-peptidase gene scpB and IS1548 associated with the hylB gene, and prophage DNA fragments F5, F7, and F10. Positive-control strains for PCR were included as described previously (8,15).…”