RESUMEN
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.
Asunto(s)
Acetiltransferasas/biosíntesis , Expresión Génica , Variación Genética , Ácido N-Acetilneuramínico/metabolismo , Streptococcus agalactiae/genética , Streptococcus agalactiae/metabolismo , Transcripción Genética , Técnicas de Tipificación Bacteriana , Análisis por Conglomerados , Electroforesis en Gel de Campo Pulsado , Femenino , Perfilación de la Expresión Génica , Genotipo , Humanos , Recién Nacido , Tipificación de Secuencias Multilocus , Embarazo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Streptococcus agalactiae/clasificación , Streptococcus agalactiae/aislamiento & purificación , Vagina/microbiologíaAsunto(s)
Portador Sano , Infecciones por Enterobacteriaceae/epidemiología , Infecciones por Enterobacteriaceae/transmisión , Enterobacteriaceae/enzimología , beta-Lactamasas/metabolismo , Factores de Edad , Anciano , Anciano de 80 o más Años , Envejecimiento , Antibacterianos/uso terapéutico , Cefotaxima/uso terapéutico , Distribución de Chi-Cuadrado , Reservorios de Enfermedades , Pruebas Antimicrobianas de Difusión por Disco , Enterobacteriaceae/efectos de los fármacos , Enterobacteriaceae/aislamiento & purificación , Infecciones por Enterobacteriaceae/tratamiento farmacológico , Infecciones por Enterobacteriaceae/microbiología , Heces/microbiología , Femenino , Francia/epidemiología , Hogares para Ancianos , Humanos , Cuidados a Largo Plazo , Masculino , Persona de Mediana Edad , Prevalencia , Orina/microbiología , Resistencia betalactámicaAsunto(s)
Bacteriemia/epidemiología , Infecciones Estafilocócicas/epidemiología , Staphylococcus aureus/clasificación , Staphylococcus aureus/genética , Zoonosis/epidemiología , Animales , Bacteriemia/microbiología , Técnicas de Tipificación Bacteriana , Francia/epidemiología , Genotipo , Humanos , Tipificación Molecular , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/aislamiento & purificación , Porcinos/microbiología , Zoonosis/microbiologíaRESUMEN
At a nursing home in France, 1 year after a first case of a cluster of urinary tract infections caused by an extended-spectrum beta-lactamase-producing strain of Escherichia coli, 9 (22%) of 49 residents were colonized with the outbreak strain. Colonization was associated with poor state of health (P = .04), incontinence (P = .007), and recent treatment with fluoroquinolones and/or cephalosporins (P = .003).