LabPasteur / Objetivos deste estudo: identificar a prevalÃncia e os fatores de risco da colonizaÃÃo materna e infecÃÃo neonatal por streptococcus do grupo B (SGB), em mulheres com trabalho de parto prematuro (TPP) e/ou ruptura prematura de membranas (RPM); medir e comparar taxas de colonizaÃÃo vaginal e anorretal por SGB, comparar taxas de detecÃÃo do SGB em meio de cultura seletivo (Todd-Hewitt) e nÃo seletivo (Stuart) e com cultivo em Ãgar-sangue e Ãgar- CPS. Estudo transversal de 112 mulheres e 220 recÃm-nascidos realizou-se na Maternidade Escola Assis Chateaubriand da Universidade federal do Cearà (MEAC-UFC), de maio de 2008 a julho de 2009. Amostras vaginais e anorretais foram colhidas de cada mulher, usando swabs estÃreis. Em 71 mulheres, 2 swabs (vaginal e anorretal), colocaram-se separadamente em meio de transporte Stuart e 2 swabs (vaginal e anorretal), inocularam-se separadamente em meio seletivo Todd-Hewitt, todos subcultivados em placas de Ãgar-sangue. Outras gestantes do grupo, 41 mulheres, foram investigadas somente em meio seletivo com subcultivo em placas de Ãgar-CPS. Colheu-se hemocultura de cada recÃm-nascido pretermo com algum sinal de infecÃÃo. A taxa de colonizaÃÃo materna de 71 mulheres foi de 4,2% e do grupo de 41, de 17%. Meio seletivo Todd-Hewitt detectou 4,4% e meio nÃo seletivo, 7,2% das culturas positivas para SGB no grupo de 71 mulheres, resultados sem diferenÃa significativa. Amostras vaginais tiveram taxas de detecÃÃo de 10,7% e anorretais de 7,1%, nÃo alcanÃando significÃncia estatÃstica. Houve diferenÃa significativa no isolamento de SGB, entre o meio Ãgar-CPS e o Ãgar-sangue. InfecÃÃo urinÃria mostrou ser importante fator de risco (P < 0,01) e a profissÃo Do lar tambÃm associou-se significativamente com a colonizaÃÃo por SGB Dos RNs incluÃdos no estudo, nenhuma hemocultura teve resultado positivo para SGB, embora apresentassem sinais de infecÃÃo e hemogramas alterados. à possÃvel que o resultado tenha ocorrido pelo fato de que as mÃes tomaram antibiÃticos antes ou durante o trabalho de parto. As taxas de colonizaÃÃo por SGB, em nosso meio, sÃo semelhantes Ãs encontradas em outras regiÃes do Brasil, podendo ser tambÃm, aqui, agente de relevÃncia na sepse neonatal que requer, sÃrias medidas de prevenÃÃo. / The objectives of this study: to identify the prevalence and the risk factors from maternal colonization and neonatal infection from group B Streptococcus in women with preterm labor and/or premature rupture membranes. It measures and compare vaginal and anorectal colonization rates. It compare detection rates with selective and non-selective culture media and it compare detection rates with blood Ãgar and CPS Ãgar. A transversal study of 112 women and 220 newborns was performed at Maternidade Escola Assis Chateaubriand from Universidade Federal do Cearà (MEAC-UFC) from may /2008 to july/2009. Vaginal and anorectal samples from each woman were collected using sterile swabs. In 71 women two swabs (vaginal and anorectal) were placed separately in Stuart transport medium and two swabs (vaginal and anorectal) were inoculated separately in Todd-Hewitt selective medium. All subcultered in blood agar plates. The other pregnancies 41 women were investigated only in selective medium and subcultered in a CPS agar plates. A blood culture was collected from each preterm newborn that with any sign of infection. The maternal colonization rate from 71 women was of 4,2% and from the 41 women group was of 17%. Todd-Hewitt selective medium detected 4,4% and non-selective medium 7,2% GBS positive culture (not statistical relevant âNSR). Vaginal samples had a detection rate of 10,7% and anorectal samples had detection rate of 7,1% ( NSR). Urinary infection and be a housewife showed to be meaningful risk factors (p < 0,05). From the newborns studied none of them had GBS positive blood culture due to the sign of infection and altered hemogram. It,s possible that the result had occurred for the fact that the mothers had taken antibiotic before or during the labor. The GBS women colonization in our environment is similar to the other regions of Brazil. The GBS could be to here an important agent for neonatal infection disease and its necessary to take serious prevent measures.

The cervical-vaginal colonization in pregnant women favors the early-onset of neonatal infection wath may cause septicemia, meningitis and pneumonia in newborns.This study has as its objective to verify the detection rates of Streptococcus agalactiae in adult patients who were seen at Hospital Universitário de Santa Maria (HUSM), Rio Grande do Sul, in the period of 2007 to 2010. It was also carried out a data survey concerning the guides, Centers for Disease Control and Prevention, published in the years 1996, 2002 and 2010, to future prevent the neonatal disease caused by the Group B Streptococcus . It was evaluated the prevalence of vaginal and rectal S. agalactiae colonization in pregnant women at the HUSM Obstetric Center from June to December 2009. The Streptococcus agalactiae positive urine cultures from patients seen at the HUSM in the period of 2007 to 2010 were evaluated as well. This study found a prevalence of 11,11% in vaginal and rectal S. agalactiae colonization in pregnant women and, among all positive cultures (6,190/34,988), the GBS was isolated in 1,52% (94/6,190) of the samples. An equal proportion was found among pregnant and non-pregnant ones. 40,4% of these women presented a score of ≥105 Colony Forming Units per milliliter of urine (CFU/mL), 53,57% , between 104 -105 CFU/mL and 6% had a score smaller than 104 CFU/mL. All GBS which were submitted to analysis were sensitive to penicillin and ampicillin. / A colonização cérvico-vaginal pelo Streptococcus agalactiae em gestantes favorece a infecção neonatal de início precoce, podendo causar septicemia, meningite e pneumonia no neonato. O objetivo deste estudo foi verificar os índices de ocorrência da detecção do Streptococcus agalactiae em pacientes adultos atendidos no Hospital Universitário de Santa Maria (HUSM), Rio Grande do Sul, Brasil, no período de 2007 a 2010. Também foi realizado um apanhado histórico dos guias Centers for Disease Control and Prevention, publicados nos anos de 1996, 2002 e 2010, para a prevenção da doença neonatal causada por Estreptococo do grupo B. Igualmente foi avaliada a prevalência da colonização vaginal e retal pelo S. agalactiae em gestantes atendidas no Centro Obstétrico do HUSM de junho a dezembro de 2009. As uroculturas positivas para Streptococcus agalactiae dos pacientes atendidos no HUSM no período de 2007 a 2010 também foram avaliadas. Esta pesquisa encontrou uma prevalência de 11,11% da colonização vaginal-retal pelo Streptococcus agalactiae em gestantes e, entre todas as uroculturas positivas (6.190/34.898), o EGB foi isolado em 1,52% das amostras (94/6.190). Uma proporção igual foi encontrada entre as grávidas e não grávidas. 40,4% das mulheres, a contagem foi ≥105 Unidades Formadoras de Colônias/mL, 53,57%, no intervalo de 104 - 105 UFC/mL e 6% com contagem menor que 104UFC/mL. Todos os EGB, submetidos à análise, foram sensíveis à penicilina e ampicilina.

Made available in DSpace on 2015-07-22T20:49:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-30 / Introdução - Os Streptococcus agalactiae são bactérias consideradas parte da microbiota da vagina, das vias aéreas superiores e do trato intestinal, porém sua importância como patógeno humano vem crescendo no decorrer dos anos. Quando presente na vagina podem trazer sérias consequências para a mulher, podendo estar associados à infertilidade, aumentar o risco de ruptura prévia de membrana, levar a corioaminionite, endometrite, etc. e, a partir da colonização vaginal da mãe, pode também haver contaminação dos neonatos na hora do parto. Objetivo - O objetivo deste estudo foi determinar a associação dos Streptococcus agalactiae com inflamação vaginal em mulheres atendidas nos laboratórios públicos de Maceió. Material e método - Foi coletado material do terço médio distal da vagina de 1014 mulheres entre 18 e 49 anos. Um dos swabs foi utilizado para a realização de exame bacterioscópico e os outros dois swabs foram utilizados para a realização de cultura para o Streptococcus agalactiae (colocado em caldo Todd-Hewitt) e outros microrganismos, além de exame a fresco direto. A identificação dos microrganismos foi realizada de acordo com a literatura. Resultados - A frequência de colonização vaginal pelo Streptococcus agalactiae encontrada neste estudo foi de 13,9%, sendo que 98 (9,7%) culturas foram positivas somente para este microrganismo e em 43 (4,2%) o mesmo estava associado a outros microrganismos. Dentre as mulheres com cultura positiva apenas para o estreptococo, 18,9% apresentaram reação inflamatória, enquanto somente 6,7% não tinham inflamação. A proporção de reações inflamatórias observadas nas mulheres colonizadas pelo estreptococo foi comparável à de outros patógenos comumente encontrados na vagina como: Candida spp., G. vaginalis e Trichomonas spp.. Em relação ao grau de associação destes microrganismos com inflamação vaginal, verificou-se um Risco Relativo de 2,80 para o Streptococcus agalactiae, 2,01 para Candida spp., 0,55 para Gardnerella vaginalis e 19,03 para Trichomonas spp. Estes dados foram confirmados pela análise multivariada pelo método Forward Stepwise (Wald). Foi verificado que a gestação não constitui um fator de risco, bem como a idade, número de parceiros sexuais, frequência de relações sexuais, abortos e gestações anteriores. Conclusão - O estreptococo do grupo B, quando presente na vagina, mostrou ser um agente promotor de inflamação, a exemplo de outros microrganimos como Candida spp e Trichomonas spp, que são sempre valorizados quando encontrados nesse sítio. Este fato mostra que esta bactéria, ainda considerada parte da microbiota vaginal, pode ser considerada tão patogênica como outros microrganismos, havendo assim a necessidade de diferenciar quanto a um estado de simples colonização ou se a bactéria está sendo agente de processo infeccioso. / superior aerial tract, and intestinal tract microbiota, but it is growing in importance as a human pathogen throughout the last years. When it is present in vagina, it can bring serious consequences to the woman, and can be associated to infertility, improving risk of premature rupture of membrane, leading to chorioamnionitis, endometritis, etc. and from mother vaginal colonization there may be contamination of neonates during delivery. Objective - Objective of this study was to determine the association of Streptococcus agalactiae with vaginal inflammatory process in women attended in public laboratories of Maceió. Material and methods – It has been collected material in the distal medium third of the vagina of 1014 women from 18 to 49 years. One of the swabs has been used to bacterioscopic examination procedures and the other two swabs had been used for culture procedures of Streptococcus agalactiae (put in Todd-Hewitt broth) and other microorganisms, beyond the fresh direct examination. The identification of the microorganisms has been made according to literature. Results – The frequency of vaginal colonization by Streptococcus agalactiae found in this study has been of 13,9%, being 98 (9,7%) positive cultures only for this microorganism and 43 (4,2%) associated with other microorganisms. Among women with positive culture only to streptococcus, 18,9% presented inflammatory reaction, while only 6,7% didn’t have inflammation. The proportion of inflammatory reactions observed in women colonized by the streptococcus has been comparable to that of other pathogens commonly found in vagina as: Candida spp., G. vaginalis and Trichomonas spp.. In relation to the degree of association of those microorganisms with vaginal inflammatory processes, it has been verified a Relative Risk of 2,80 for Streptococcus agalactiae, 2,01 for Candida spp., 0,55 for Gardnerella vaginalis and 19,03 for Trichomonas spp. Those data have been confirmed by the multivariant analysis using Forward Stepwise method (Wald). It has been verified that pregnancy does not constitute a risk factor, nor age, number of partners, frequency of intercourse, abortions and previous pregnancies. Conclusion – B group streptococcus, when it is present in vagina showed to be an inflammatory process promoting agent, as for example other microorganisms, like Candida spp and Trichomonas spp, that are always valued when they are found in that site. This fact shows that this bacteria that is still considered as part of vaginal biota, should be considered so much pathogenic as other microorganisms, thus existing the necessity of differenciating between a state of simple colonization or otherwise if the bacteria is being an infectious process agent. / TEDE / BV UNIFESP: Teses e dissertações

Les mycoplasmes sont des bactéries atypiques, dépourvues de paroi et souvent considérées comme des cellules minimales du fait de la taille réduite de leur génome. De nombreuses espèces sont pathogènes et ont un impact économique important dans les filières d'élevage, notamment pour les ruminants. Les mycoplasmes n'échappent pas au phénomène mondial de la résistance aux antibiotiques. Contrairement à la plupart des autres bactéries, les mycoplasmes ne contiennent pas de plasmides conjugatifs souvent incriminés dans la dissémination horizontale de gènes de résistance, la base moléculaire principalement décrite étant la mutation chromosomique des gènes cibles. De façon générale, le transfert horizontal de gènes (HGT) chez les mycoplasmes a longtemps été sous-estimé. Récemment, deux mécanismes de HGT ont été décrits chez Mycoplasma agalactiae : le transfert d'élément conjugatif et intégratif (ICE), et le transfert non-conventionnel de régions chromosomiques par conjugaison appelé MCT (Mycoplasma Chromosomal Transfer). Nos travaux se sont attachés à explorer ce dernier mécanisme et à évaluer son impact sur l'acquisition de la résistance aux antibiotiques. Une analyse de génomique comparative a été conduite à partir du séquençage de nombreux mutants spontanément résistants et de transconjugants générés par des expériences de mating et sélectionnés pour leur résistance. Nos résultats montrent que le MCT conduit de façon distributive au transfert simultané de nombreux fragments. En une seule étape de conjugaison impliquant deux souches, ce phénomène génère une population variée de génomes hautement mosaïques. Il accélère la dissémination de l'antibiorésistance, permettant l'acquisition de plusieurs mutations distantes associées à la résistance en un seul événement. De par les multiples possibilités de réassemblage génomique qu'il produit, le MCT pourrait avoir des conséquences importantes sur d'autres processus adaptatifs comme la virulence ou la spécificité d'hôte. Enfin, les modalités distributives et l’ampleur du MCT expliquent l'origine des transferts de gènes précédemment détectés in silico entre de nombreux mycoplasmes. Ce phénomène pourrait donc avoir eu des répercussions importantes sur l'évolution de ces bactéries minimales et être un facteur clé de leur persistance et virulence actuelles.

Streptococcus agalactiae infection is one of the major disease problems affecting farmed tilapia (Oreochromis niloticus) worldwide. Tilapia are highly susceptible to this disease which results in mortality of up to 70% over a period of around 7 days and significant economic losses for farmers. Affected tilapia commonly present with an irregular behaviour associated with meningoencephalitis and septicaemia. Currently, factors affecting the virulence and transmission of S. agalactiae in fish including tilapia are poorly understood. Reports from natural outbreaks of S. agalactiae infection on tilapia farms have suggested larvae and juvenile or fish smaller than 20 g are not susceptible. In addition, there is variability in individual response to experimental inflammatory challenge associated with coping styles (bold, shy) in common carp (Cyprinus carpio). The central hypotheses of this thesis were that weight, age and coping style might affect the development and progression of this bacterial disease. This study investigated these three factors with experimental S. agalactiae infection in Nile tilapia. A range of bacterial isolates recovered from farmed tilapia, presenting with clinical sign of streptococcosis during natural disease outbreaks were identified and characterised as S. agalactiae by standard conventional methods, biochemical characteristic tests, Lancefield serogrouping and species-specific PCR assay. These isolates were Gram-positive cocci, either β- or non-haemolytic (γ), non-motile, oxidase negative and all of serogroup B. In addition, they were able to grow on Edwards medium (modified) agar as blue colonies and growth was observed in broth from 22 to 37 oC and with 0.5-5% NaCl. The biochemical profiles showed some differences in reactions while all the PCR samples showed similarities to the S. agalactiae type strain. These data confirmed that these strains were identified as group B S. agalactiae. A challenge model for S. agalactiae in Nile tilapia was developed and the LD50 estimated prior to performing subsequent experimental challenge studies. Two exposure routes, immersion and intraperitoneal injection (i.p.), were tested with various concentrations of S. agalactiae. Only i.p. injection produced significant mortalities (9 × 108 CFU/ml = 48% mortality, 9 × 107 = 48% and 8 × 106 = 26%). Streptococcus agalactiae was recovered and identified from all the dead and moribund fish during these experiments, where affected fish showed similar clinical signs and pathology to those reported from natural S. agalactiae infections. The study results showed that an experimental i.p. challenge model for S. agalactiae infection had successfully infected healthy Nile tilapia. In the immersion challenges, only 1 fish died despite testing a range of bacterial concentrations, exposure times, stocking density, water system and bacterial preparations. The experimental studies were conducted to investigate the association between weight or age of fish and susceptibility to S. agalactiae infection in Nile tilapia. This was performed under experimental conditions including control groups and a single population of 8 months old fish from one set of parents divided into 7 weight categories. These fish received a single i.p. injection of 6 × 107 CFU/ml of S. agalactiae. Controls and fish of 4 or 8 months old with a mean weight of 5 g received an i.p. injection of 7 × 107 CFU/ml of S. agalactiae. Clinical signs, lesions and histopathological changes in the affected fish were consistent with those reported in natural infection. Streptococcus agalactiae was recovered and identified from all moribund or dead fish. The mortality in the study of different weights varied from 0 to 33% between the groups but the association with weight was weak (R2 = 0.02). In the study of different ages the 4 months old fish group had a total mortality of 24%, and the 8 months old fish group a total mortality of 4%. This study produced no evidence for an association between the weight and susceptibility to S. agalactiae infection but suggested an association between the age or growth rate of fish and this disease. Different coping styles and susceptibility to S. agalactiae infection in Nile tilapia was examined. Fish were screened and scored depending on their risk-taking behavioural responses to a range of different environmental conditions. Individual differences in behavioural responses were evident but only consistent across behavioural trials for some individuals. A selection of fish with consistent responses across trials was exposed to the 6 × 107 CFU/ml of S. agalactiae by i.p. injection. Fewer bold than shy fish died suggesting that the bold fish might be less susceptible to the infection than shy fish. In conclusion, this study characterised a number of S. agalactiae isolates and developed an experimental bacterial challenge model. Subsequent experiments suggested that age (or growth rate) and coping style in fish but not the fish weight may affect susceptibility to S. agalactiae infection in Nile tilapia.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 6 uppsatser.

Thesis (Ph. D.)--University of Sydney, 2004. / Title from title screen (viewed 8 May 2008). A reference list of published articles is provided in Appendices. Includes copies of seven published papers, co-authored by Fanrong Kong. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Dept. of Medicine. Includes bibliographical references. Also available in print form.

VENTURA, Maria Sidneuma Melo. Colonização em gestantes e infecção neonatal por Streptococcus do grupo B. 2009. 69 f. Dissertação (Mestrado em Saúde Pública) - Universidade Federal do Ceará, Fortaleza, 2009. / Submitted by denise santos (denise.santos@ufc.br) on 2011-11-08T13:21:42Z No. of bitstreams: 1 2009_dis_msmventura.pdf: 104830 bytes, checksum: 884e55cddb6fb4624b7bfa5f83de382d (MD5) / Approved for entry into archive by Eliene Nascimento(elienegvn@hotmail.com) on 2011-12-05T12:23:26Z (GMT) No. of bitstreams: 1 2009_dis_msmventura.pdf: 104830 bytes, checksum: 884e55cddb6fb4624b7bfa5f83de382d (MD5) / Made available in DSpace on 2011-12-05T12:23:26Z (GMT). No. of bitstreams: 1 2009_dis_msmventura.pdf: 104830 bytes, checksum: 884e55cddb6fb4624b7bfa5f83de382d (MD5) Previous issue date: 2009 / The objectives of this study: to identify the prevalence and the risk factors from maternal colonization and neonatal infection from group B Streptococcus in women with preterm labor and/or premature rupture membranes. It measures and compare vaginal and anorectal colonization rates. It compare detection rates with selective and non-selective culture media and it compare detection rates with blood ágar and CPS ágar. A transversal study of 112 women and 220 newborns was performed at Maternidade Escola Assis Chateaubriand from Universidade Federal do Ceará (MEAC-UFC) from may /2008 to july/2009. Vaginal and anorectal samples from each woman were collected using sterile swabs. In 71 women two swabs (vaginal and anorectal) were placed separately in Stuart transport medium and two swabs (vaginal and anorectal) were inoculated separately in Todd-Hewitt selective medium. All subcultered in blood agar plates. The other pregnancies 41 women were investigated only in selective medium and subcultered in a CPS agar plates. A blood culture was collected from each preterm newborn that with any sign of infection. The maternal colonization rate from 71 women was of 4,2% and from the 41 women group was of 17%. Todd-Hewitt selective medium detected 4,4% and non-selective medium 7,2% GBS positive culture (not statistical relevant –NSR). Vaginal samples had a detection rate of 10,7% and anorectal samples had detection rate of 7,1% ( NSR). Urinary infection and be a housewife showed to be meaningful risk factors (p < 0,05). From the newborns studied none of them had GBS positive blood culture due to the sign of infection and altered hemogram. It,s possible that the result had occurred for the fact that the mothers had taken antibiotic before or during the labor. The GBS women colonization in our environment is similar to the other regions of Brazil. The GBS could be to here an important agent for neonatal infection disease and its necessary to take serious prevent measures. / Objetivos deste estudo: identificar a prevalência e os fatores de risco da colonização materna e infecção neonatal por streptococcus do grupo B (SGB), em mulheres com trabalho de parto prematuro (TPP) e/ou ruptura prematura de membranas (RPM); medir e comparar taxas de colonização vaginal e anorretal por SGB, comparar taxas de detecção do SGB em meio de cultura seletivo (Todd-Hewitt) e não seletivo (Stuart) e com cultivo em ágar-sangue e ágar- CPS. Estudo transversal de 112 mulheres e 220 recém-nascidos realizou-se na Maternidade Escola Assis Chateaubriand da Universidade federal do Ceará (MEAC-UFC), de maio de 2008 a julho de 2009. Amostras vaginais e anorretais foram colhidas de cada mulher, usando swabs estéreis. Em 71 mulheres, 2 swabs (vaginal e anorretal), colocaram-se separadamente em meio de transporte Stuart e 2 swabs (vaginal e anorretal), inocularam-se separadamente em meio seletivo Todd-Hewitt, todos subcultivados em placas de ágar-sangue. Outras gestantes do grupo, 41 mulheres, foram investigadas somente em meio seletivo com subcultivo em placas de ágar-CPS. Colheu-se hemocultura de cada recém-nascido pretermo com algum sinal de infecção. A taxa de colonização materna de 71 mulheres foi de 4,2% e do grupo de 41, de 17%. Meio seletivo Todd-Hewitt detectou 4,4% e meio não seletivo, 7,2% das culturas positivas para SGB no grupo de 71 mulheres, resultados sem diferença significativa. Amostras vaginais tiveram taxas de detecção de 10,7% e anorretais de 7,1%, não alcançando significância estatística. Houve diferença significativa no isolamento de SGB, entre o meio ágar-CPS e o ágar-sangue. Infecção urinária mostrou ser importante fator de risco (P < 0,01) e a profissão Do lar também associou-se significativamente com a colonização por SGB Dos RNs incluídos no estudo, nenhuma hemocultura teve resultado positivo para SGB, embora apresentassem sinais de infecção e hemogramas alterados. É possível que o resultado tenha ocorrido pelo fato de que as mães tomaram antibióticos antes ou durante o trabalho de parto. As taxas de colonização por SGB, em nosso meio, são semelhantes às encontradas em outras regiões do Brasil, podendo ser também, aqui, agente de relevância na sepse neonatal que requer, sérias medidas de prevenção.

Dissertação (mestrado) - Pontifícia Universidade Católica do Paraná, Curitiba, 2009. / Bibliografia: 110-127. / Nos últimos quarenta anos, estreptococos do grupo B (EGB) têm sido descrito como relevante patógeno em infecções invasivas neonatais, e atualmente, em pacientes senis ou com condições debilitantes. A terapia antimicrobiana intraparto continua sendo a prin / In the last forty years, group B streptococci (GBS) have been described as an important pathogen in neonatal invasive infections, and currently, in elderly or adults with underlying medical conditions. Intrapartum hemoprophylaxis remains the main measure

Nous avons étudié le rôle des éléments génétiques mobiles (EGM) dans l’évolution et la virulence de Streptococcus agalactiae, bactérie pathogène opportuniste responsable d'infections chez l’homme. La structure génétique de la population a été analysée par multilocus sequence typing à partir d’un souchier représentatif de la diversité de l’espèce. La distribution de 11 EGM (sept séquences d’insertion, trois transposases, un intron) a été confrontée à la structure de la population. Cette confrontation a permis i) de démontrer que l’acquisition des EGM corrélait avec l’évolution de l’espèce, ii) de proposer une hypothèse de la chronologie d’acquisition des EGM, iii) d’identifier certains EGM comme marqueurs de l’écosystème d’origine des souches, et iv) de conforter l’hypothèse de l’émergence du clone humain invasif CC17 à partir d’un ancêtre bovin. Nous avons également cartographié les copies des EGM présentes sur le génome de S. agalactiae, puis nous avons identifié huit nouveaux sites d’insertion, dont deux sont significativement associés à l’origine écologique de la souche. / We studied the role of mobile genetic elements (MGE) on the evolution and the virulence of Streptococcus agalactiae, an opportunistic bacterium responsible for human infections. The genetic population structure was analyzed by multilocus sequence typing using a collection representative of the species diversity. The distribution of 11 MGE (seven insertion sequences, three transposases, one intron) was compared to the population structure. We demonstrated that the MGE prevalence strongly correlates with the genetic lineages. We proposed an evolutionary scheme for the acquisition of the MGE. Several MGE appeared to be markers of the origin of the strains. MGE analysis brought evidence for a bovine origin of the human virulent clone CC17. We also identified the position of the MGE copies on the S. agalactiae genome and we identified eight new MGE insertion sites, from which two were significantly associated with the ecological origin of the isolates.