La première partie de nos travaux a consisté au séquençage de génomes complets de trois souches pathogènes et de trois souches de portage de Staphylococcus lugdunensis pour les comparer aux 15 génomes complets disponibles sur NCBI. Aucun déterminant génétique associé au contexte de virulence ou de portage de S. lugdunensis n’a été identifié. Cependant, nous avons mis en évidence la présence d’éléments génétiques mobiles et des variations dépendantes des complexes clonaux,définis par MultiLocus Sequence Typing, au sein de loci potentiellement associés à la virulence. Des variations ont été observées dans un locus homologue à celui de Staphylococcus aureus codant le système de sécrétion Ess/type VII (SST7). Nous avons mis en évidence huit organisations génétiques chez cette espèce présentant pourtant une structure de population clonale. La seconde partie de nos travaux a consisté à la caractérisation phénotypique et moléculaire du SST7 chez S. lugdunensis par la formation d’un mutant de délétion du gène essC codant une protéine essentielle à la sécrétion. Nos résultats suggèrent que le SST7 serait impliqué dans la translocation de protéines prédites in silico comme impliquées dans la virulence. Néanmoins, dans des modèles de cytotoxicité cellulaire et d’infection du nématode Caenorhabditis elegans, aucune atténuation de la virulence n’a été observée chez la souche mutante malgré une perte de sa capacité à lyser les erythrocytes, comparativement à la souche sauvage. Nos travaux ont également permis de développer et d’évaluer le pouvoir discriminant de trois nouvelles méthodes de typage constituant des outils très prometteurs pour l’épidémiologie moléculaire des infections à S. lugdunensis. / The first part of this study consisted in whole genome sequencing of three pathogenic and three carriage strains of S. lugdunensis and comparison with the 15 genomes available in the NCBI. No genetic determinant was associated to the pathogenic or carriage context. However, we have highlighted the presence of mobile genetic elements and MultiLocus Sequence Typing clonal complex dependent variations within loci potentially associated with virulence. Variations wereobserved in the ess locus homologous to that of Staphylococcus aureus encoding the type VII secretion system (T7SS). We showed eight genetic organizations in this species with a clonal population structure. The second part of our work consisted in a phenotypic and molecular characterization of T7SS in S. lugdunensis by construction of a deletion essC gene mutant. This gene encodes a protein requiredfor protein secretion. Our results suggest that T7SS could be involved in translocation of proteins predicted as implicated in virulence in silico. Nevertheless, no virulence attenuation was observed in cells cytotoxicity assay and Caenorhabditis elegans virulence assays between wild-type and mutant strains which yet has lost the ability to lyse erythrocytes. We also developed and evaluated discriminating power of three new typing methods, which are very promising tools for the molecular epidemiology of S. lugdunensis infections.

Introduction: Colonization of the anogenital tract of pregnant women by Group B Streptococcus (GBS) is the main risk factor for early-onset neonatal sepsis. Identification of maternal colonization allows antimicrobial prophylaxis and prevention of vertical transmission. Objectives: To identify the genetic diversity and phenotypic characteristics of GBS using molecular biology techniques and culture in specific medium, and the epidemiological aspects of pregnant women colonized by this bacterium. Methods: It was performed a cross-sectional study, anogenital samples of 316 pregnant women were collected between 35 and 37 weeks and submited to culture in specific medium, antimicrobial susceptibility test, multiplex PCR, multi locus sequence typing (MLST) and multi locus variable number of tandem repeat analysis (MLVA). The epidemiological aspects of colonized and non-colonized pregnant women were also investigated. Results: It was obtained a prevalence of 36.4% by culture and 38.6% by PCR. Multiplex PCR had sensitivity of 100%, specificity of 96.5%, positive predictive value of 94.3% and negative predictive value of 100%. The most common serotypes were Ia, V, II and III. Resistance genes were identified in 34 samples. Sensitivity to penicillin was universal, 24.3% presented resistance to erythromycin and 14.8% to clindamycin. Evaluating the epidemiological variables, there were no differences between the colonized and non-colonized pregnant women. Diversity index and number of genotypes found by MLST was 0.608 and 6, and by MLVA was 0.840 and 15, respectively. Conclusion: We found a high prevalence of maternal GBS colonization, with serotype distribution similar to the Americas region. Multiplex PCR was more accurate than culture, and maternal epidemiological variables showed no difference when evaluating presence or absence of bacterial colonization, its serotypes and antimicrobial resistance. MLVA showed a higher discrimination capacity among the unrelated strains than MLST. / Submitted by Otto Henrique May Feuerschuette (otto.feurschuette@unisul.br) on 2018-04-26T00:54:22Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) OTTO TESE CORRIGIDA PÓS BANCA (1).pdf FINAL.pdf: 3081595 bytes, checksum: afad5beba2687558aafe2f1705d36e01 (MD5) / Approved for entry into archive by Silvane Cauz (silvane.cauz@unisul.br) on 2018-04-26T12:14:53Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) OTTO TESE CORRIGIDA PÓS BANCA (1).pdf FINAL.pdf: 3081595 bytes, checksum: afad5beba2687558aafe2f1705d36e01 (MD5) / Made available in DSpace on 2018-04-26T12:14:53Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) OTTO TESE CORRIGIDA PÓS BANCA (1).pdf FINAL.pdf: 3081595 bytes, checksum: afad5beba2687558aafe2f1705d36e01 (MD5) Previous issue date: 2018 / Introdução: A colonização do trato anogenital de gestantes pelo Estreptococo do grupo B (EGB) é o fator de risco primário para a sepse neonatal precoce. A identificação da colonização materna permite a profilaxia antimicrobiana e prevenção da transmissão vertical. Objetivos: Identificar a diversidade genética e as características fenotípicas do EGB utilizando-se técnicas de biologia molecular e cultura em meio específico, e avaliar os aspectos epidemiológicos de gestantes colonizadas por essa bactéria Métodos: Foi realizado um estudo transversal com 316 amostras anogenitais de gestantes entre 35 e 37 semanas para realização de cultura em meio específico, teste de sensibilidade aos antimicrobianos, PCR multiplex, multi locus sequence typing (MLST) e multi locus variable number of tandem repeat analysis (MLVA). Pesquisou-se também os aspectos epidemiológicos dessas gestantes. Resultados: Foi encontrada prevalência de 36,4% pela cultura e 38,6% pela PCR. A PCR multiplex apresentou sensibilidade de 100%, especificidade de 96,5%, valor preditivo positivo de 94,3% e valor preditivo negativo de 100%. Os sorotipos mais encontrados foram Ia, V, II e III. Os genes de resistência foram identificados em 34 amostras. A sensibilidade à penicilina foi universal, 24,3% apresentaram resistência à eritromicina e 14,8% à clindamicina. Avaliando-se as variáveis epidemiológicas, não se identificaram diferenças entre as gestantes colonizadas e não colonizadas. O índice de diversidade e o número de genogrupos encontrados pelo MLST foi 0,608 e 6, e pela MLVA foi 0,840 e 15, respectivamente Conclusão: Constatou-se uma alta prevalência de colonização materna, com distribuição dos sorotipos semelhante à região das Américas. A PCR multiplex foi mais acurada que a cultura, e as variáveis epidemiológicas maternas não apresentaram diferença significativa ao avaliar-se a presença ou não de colonização bacteriana, seus sorotipos e a resistência aos antimicrobianos. A MLVA apresentou uma capacidade de discriminação entre as cepas não relacionadas maior do que a MLST