title: Variability of neuD transcription levels and capsular sialic acid expression among serotype III group B Streptococcus strains.
abstract: Serotype III group B Streptococcus (GBS) is the major cause of neonatal meningitis, but the risk of infection in the colonized neonates is variable. Capsular sialic acid (Sia), whose synthesis is encoded by neu genes, appears to be a major virulence factor in several bacterial species able to reach the cerebrospinal fluid. Therefore, variations of Sia expression related to the genetic diversity of strains may have an impact on the risk of meningitis in colonized neonates. We characterized by MLST the phylogenetic diversity of 64 serotype III GBS strains isolated from vaginal flora and randomly selected. These strains mostly belonged to three major sequence types (STs): ST1 (11%), ST17 (39%) and ST19 (31%). The genetic diversity of strains of these lineages, characterized by PFGE, allowed the selection of 17 representative strains, three ST1, six ST17 and eight ST19, with NEM316 as reference, in order to evaluate (i) by quantitative RT-PCR, the level of transcription of the neuD gene as a marker for the transcription of neu genes and (ii) by enzymological analysis, the expression of Sia. The mean transcription level of neuD was higher for ST17 strains than for ST1 and ST19 strains in the early, mid- and late exponential growth phases, and was maximum in the early exponential growth phase for ST17 strains and in the mid-exponential growth phase for ST1 and ST19 strains. Mean Sia concentration was higher for ST17 than for ST1 and ST9 strains in all three growth phases. For the total population, Sia concentration varied notably in the stationary phase, from 0.38 to 9.30 nmol per 10(8) viable bacteria, with a median value of 2.99 nmol per 10(8) bacteria. All ST17 strains, only one-third of the ST19 strains and none of the ST1 strains had Sia concentrations higher than the median Sia concentration. Therefore, differences in the level of expression of Sia by strains of the major serotype III GBS phylogenetic lineages might be one of the factors that explain the leading role of ST17 strains in neonatal meningitis.
authors.affiliation: Service de Bactériologie et Hygiène Hospitalière, Hôpital Trousseau, CHRU de Tours, 37044 Tours, France.|Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Marie-Frédérique
authors.initials: MF
authors.lastname: Lartigue
authors.affiliation: Service de Bactériologie et Hygiène Hospitalière, Hôpital Trousseau, CHRU de Tours, 37044 Tours, France.|Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Agnès Fribourg
authors.initials: AF
authors.lastname: Poulard
authors.affiliation: Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Rim
authors.initials: R
authors.lastname: Al Safadi
authors.affiliation: Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Pailhories
authors.affiliation: Service de Bactériologie et Hygiène Hospitalière, Hôpital Trousseau, CHRU de Tours, 37044 Tours, France.|Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Domelier-Valentin
authors.affiliation: Service de Bactériologie et Hygiène Hospitalière, Hôpital Trousseau, CHRU de Tours, 37044 Tours, France.|Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: van der Mee-Marquet
authors.affiliation: Service de Bactériologie et Hygiène Hospitalière, Hôpital Trousseau, CHRU de Tours, 37044 Tours, France.|Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Rosenau
authors.affiliation: Service de Bactériologie et Hygiène Hospitalière, Hôpital Trousseau, CHRU de Tours, 37044 Tours, France.|Université François-Rabelais de Tours, UFR de Médecine, EA 3854 'Bactéries et Risque Materno-foetal', Institut Fédératif de Recherche 136 'Agents Transmissibles et Infectiologie', 37032 Tours Cedex, France.
authors.forename: Roland
authors.initials: R
authors.lastname: Quentin
mesh_terms: D000123:Acetyltransferases / Q000096:biosynthesis*; D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007231:Infant, Newborn; D058885:Multilocus Sequence Typing; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013292:Streptococcus agalactiae / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic; D014621:Vagina / Q000382:microbiology
chemical_list: D000123:Acetyltransferases; D019158:N-Acetylneuraminic Acid