Ultrastructural Alterations of Term Human Amnionic Epithelium Following Incubation With Group B Beta‐Hemolytic Streptococci

Mw, Varner; Jw, Turner; Cr, Petzold; Rp, Galask

doi:10.1111/j.1600-0897.1985.tb00308.x

Cited by 7 publications

(8 citation statements)

References 6 publications

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“…A frequent cause of S. agalactiae infection is aspiration of infected amniotic fluid by the fetus. Amniotic fluid only has low titers of antibody against S. agalactiae (20) and supports growth of S. agalactiae to high cell densities (14,66). As the present study demonstrates an important role of DpsA for growth of S. agalactiae in amniotic fluid, DpsA represents an interesting target for the prevention or treatment of in utero S. agalactiae infections.…”

Section: Discussionmentioning

confidence: 96%

“…The dpsA gene plays an important role during growth in amniotic fluid. S. agalactiae is known to infect the placenta and grow in amniotic fluid to high cell densities (15,50,66). The importance of peptide uptake for growth of S. agalactiae in amniotic fluid was studied with the strain O90R and the triple mutant ⌬dppB ⌬oppB ⌬dpsA.…”

Section: Resultsmentioning

confidence: 99%

“…A common cause of neonatal infection is the colonization of the human rectovaginal tract with S. agalactiae, ascending spread of the bacteria into the amniotic fluid, and aspiration of contaminated amniotic fluid by the infant (8). Although amniotic fluid contains only low amounts of free amino acids (35), it supports growth of S. agalactiae to high concentrations (14,66), indicating that S. agalactiae satisfies its amino acid requirements in amniotic fluid by the uptake of peptides.…”

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confidence: 99%

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Relevance of Peptide Uptake Systems to the Physiology and Virulence of Streptococcus agalactiae

et al. 2004

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Streptococcus agalactiae is a major cause of invasive infections in human newborns. To satisfy its growth requirements, S. agalactiae takes up 9 of the 20 proteinogenic amino acids from the environment. Defined S. agalactiae mutants in one or several of four putative peptide permease systems were constructed and tested for peptide uptake, growth in various media, and expression of virulence traits. Oligopeptide uptake by S. agalactiae was shown to be mediated by the ABC transporter OppA1-F, which possesses two substrate-binding proteins (OppA1 and OppA2) with overlapping substrate specificities. Dipeptides were found to be taken up in parallel by the oligopeptide permease OppA1-F, by the dipeptide ABC transporter DppA-E, and by the dipeptide symporter DpsA. Reverse transcription-PCR analysis revealed a polycistronic organization of the genes oppA1-F and dppA-E and a monocistronic organization of dpsA in S. agalactiae. The results of quantitative real-time PCR revealed a medium-dependent expression of the operons dppA-E and oppA1-F in S. agalactiae. Growth of S. agalactiae in human amniotic fluid was shown to require an intact dpsA gene, indicating an important role of DpsA during the infection of the amniotic cavity by S. agalactiae. Deletion of the oppB gene reduced the adherence of S. agalactiae to epithelial cells by 26%, impaired its adherence to fibrinogen and fibronectin by 42 and 33%, respectively, and caused a 35% reduction in expression of the fbsA gene, which encodes a fibrinogen-binding protein in S. agalactiae. These data indicate that the oligopeptide permease is involved in modulating virulence traits and virulence gene expression in S. agalactiae.Streptococcus agalactiae has a limited capacity to synthesize amino acids and must acquire from the environment 9 of the 20 proteinogenic amino acids for growth (38). The amino acid requirements of S. agalactiae can be satisfied by the uptake of peptides, which are cleaved in the cytoplasm to their respective amino acids (69, 70). In microorganisms, two different peptide uptake systems have been described (23, 41). The most common peptide transporters are binding-protein-dependent permeases, consisting of multiple components, belonging to the ATP-binding cassette (ABC) transporter superfamily (24). The process of peptide transport by ABC transporters involves the extracytoplasmic binding of the substrate by a substrate-binding protein, transfer of the substrate to two membrane-integrated permeases for translocation across the cytoplasmic membrane, and ATP hydrolysis by one or two proteins located on the cytoplasmic side of the membrane (24). In numerous bacteria, the uptake of di-and oligopeptides is mediated by these ABC transporters (41). In contrast, some microorganisms take up diand/or tripeptides by single proteins with similarity to eukaryotic peptide transport proteins of the PRT family (62). These bacterial permeases use the proton motive force across the cytoplasmic membrane for the uptake of peptides (23, 37). They exhibit a broad substrate spec...

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Section: Discussionmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Relevance of Peptide Uptake Systems to the Physiology and Virulence of Streptococcus agalactiae

et al. 2004

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“…Neonatal deaths which have resulted from bacterial amniotic fluid infections can occur with apparently intact chorioamnionic membranes (31). Several investigators have hypothesized that GBS may actively invade through the placental membrane, resulting in growth of the organism in the amniotic fluid (9,30,46); however, this has not been confirmed to date.…”

Section: Discussionmentioning

confidence: 99%

“…Colonization of the human rectovaginal tract with GBS is a risk factor associated with chorioamnionitis, premature rupture of the placental membrane, and transmission to the infant (3,4,34). Amniotic fluid infections have occurred through apparently intact chorioamnionic membranes (31), and it has been suggested that the organism may actively invade through intact placental membranes and grow to high concentrations in the amniotic fluid (9,46). Neonatal exposure to high concentrations of GBS in utero leads to colonization of the lung airways and subsequent pneumonia, sepsis, and meningitis (38).…”

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confidence: 99%

Characterization of Group B Streptococcal Invasion of Human Chorion and Amnion Epithelial Cells In Vitro

et al. 1998

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Group B streptococci (GBS) have been cultured from the chorioamnionic membrane of pregnant women, usually in association with chorioamnionitis and premature labor (K. A. Boggess, D. H. Watts, S. L. Hillier, M. A. Krohn, T. J. Benedetti, and D. A. Eschenbach, Obstet. Gynecol. 87:779–784, 1996). Colonization and infection of placental membranes can be a prelude to neonatal GBS infections even in the presence of intact membranes (R. L. Naeye and E. C. Peters, Pediatrics61:171–177, 1978), suggesting that GBS cause chorioamnionitis or establish amniotic fluid infections by partial or complete penetration of the placental membranes. We have isolated and grown cultures of primary chorion and amnion cells from human cesarean-section placentas. This has provided a biologically relevant model for investigating GBS adherence to and invasion of the two epithelial barriers of the placental membrane. GBS adhered to chorion cell monolayers to a high degree. Pretreatment of GBS with trypsin reduced adherence up to 10-fold, which suggested that the bacterial ligand(s) was a protein. GBS invaded chorion cells at a high rate in vitro, and invasion was dependent on cellular actin polymerization. GBS could be seen within intracellular vacuoles of chorion cells by transmission electron microscopy. We also demonstrated that GBS were capable of transcytosing through intact chorion cell monolayers without disruption of intracellular junctions. GBS also adhered to amnion cells; in contrast, however, these bacteria failed to invade amnion cells under a variety of assay conditions. GBS interactions with the chorion epithelial cell layer shown here correlate well with epidemiological and pathological studies of GBS chorioamnionitis. Our data also suggest that the amnion cell layer may provide an effective barrier against infection of the amniotic fluid.

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In vitro systems for investigating group B streptococcal: host cell and extracellular matrix interactions

Winram

Tamura

Rubens

1998

Methods for Studying the Genetics, Molecular Biology, Physiology, and Pathogenesis of the Streptococci

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Ultrastructural Alterations of Term Human Amnionic Epithelium Following Incubation With Group B Beta‐Hemolytic Streptococci

Cited by 7 publications

References 6 publications

Relevance of Peptide Uptake Systems to the Physiology and Virulence of Streptococcus agalactiae

Relevance of Peptide Uptake Systems to the Physiology and Virulence of Streptococcus agalactiae

Characterization of Group B Streptococcal Invasion of Human Chorion and Amnion Epithelial Cells In Vitro

In vitro systems for investigating group B streptococcal: host cell and extracellular matrix interactions

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