Aeromonas spp. são bactérias Gram negativas capazes de causar doenças intestinais e extra-intestinais. A virulência de algumas espécies do gênero já foi associada a diversos fatores, como a expressão de flagelos e conseqüente mobilidade bacteriana. Aeromonas caviae apresenta dois distintos sistemas flagelares, um deles responsável pela natação em meio líquido (swimming) onde está envolvido o flagelo polar, e outro associado ao deslizamento em superfícies sólidas ou viscosas (swarming), o qual participam flagelos laterais. A fim de avaliar a contribuição de ambos os flagelos no contexto da formação de biofilme em superfície plástica e aderência à linhagem celular HEp-2, foram estudadas 76 cepas de A. caviae isoladas de diferentes origens. Os resultados obtidos em nosso estudo demonstraram que a detecção do gene flaA (flagelina polar) foi mais freqüente (94%) que a do gene lafA (flagelina lateral) (71%) e, aparentemente, a presença deste último parece estar condicionada à do primeiro. Todas as cepas que apresentaram o genótipo flaA-lafA-, foram incapazes de formar biofilme, bem como 76% das cepas flaA+lafA-. As cepas provenientes de água foram as que exibiram menor percentual de positividade para o gene da flagelina lateral (57%) e aquelas onde se observou maior incapacidade de formação de biofilme (71%). Além disso, 95% das cepas flaA+lafA+ formaram biofilme e todas as cepas que apresentaram, quantitativamente, um biofilme forte, albergavam ambos os genes. A aderência à HEp-2 se mostrou eficiente em todos os casos onde ao menos um dos flagelos estava presente e em dois casos onde ambos estavam ausentes, com prevalência do padrão agregativo. Em contrapartida, não foi notado uma interferência exclusiva dos flagelos laterais nesse processo. Todas as três cepas que não aderiram ao modelo celular utilizado, ou o fizeram muito discretamente, não exibiram nem o gene flaA, tampouco lafA. Em conclusão aos dados observados, apontamos que uma plena atividade de ambos os flagelos, geralmente, é requerida nos processos de aderência às superfícies abióticas e bióticas. Contudo, trabalhos adicionais sobre a contribuição dessas estruturas na patogênese de A. caviae necessitam ser realizados. / Aeromonas spp. are bacteria Gram-negative able to cause intestinal and extraintestinal diseases. The virulence of some species of this genus has already been associated to several aspects, such as the expression of flagellum and following bacterium mobility. Aeromonas caviae presents two distinct flagellar systems, one of which is responsible for mobility in liquid environments (swimming) at where the polar flagellum is involved, and the other is associated to sliding in solid or viscous surfaces (swarming), in which lateral flagella take part. In order to evaluate the contribution of both flagella in the biofilm formation in plastic surfaces and its adherence to cell line HEp-2, 76 strains of isolated A. caviae from distinct sources were analyzed. The results from our studies showed that detection of gene flaA (polar flagellin) was more frequent (94%) than gene lafA (lateral flagellin) (71%), and apparently, the presence of the last one seems to be conditioned to the first one (the gene flaA). All the strains that presented the genotype flaA-lafA- were unable to form biofilm, such as 76% of strains flaA+lafA-. The aquatic strains were those who showed lesser percentage of positivity for the lateral flagellin gene (57%), and higher incapacity of biofilm formation (71%). Moreover, 95% of the flaA+lafA+ strains formed biofilm, and all strains that quantitatively showed a strong biofilm, contained both genes. The adherence to HEp-2 proved to be efficient in all cases where at least one of the two flagella was present at, and in two cases where both were absent, with prevalence of the aggregative pattern. However, an exclusive interference from the lateral flagella was not perceived in this process. All of the three strains that did not adhere to the cell model used, or that adhered in a very discrete way, did not show neither gene flaA nor gene lafA. In conclusion, we suggest that the complete function of both flagella usually is a requirement in the adherence processes to biotic and abiotic surfaces. However, additional studies on the contribution of these structures in the pathogenesis of A. caviae need to be carried out.

Aeromonas spp. são bactérias Gram negativas capazes de causar doenças intestinais e extra-intestinais. A virulência de algumas espécies do gênero já foi associada a diversos fatores, como a expressão de flagelos e conseqüente mobilidade bacteriana. Aeromonas caviae apresenta dois distintos sistemas flagelares, um deles responsável pela natação em meio líquido (swimming) onde está envolvido o flagelo polar, e outro associado ao deslizamento em superfícies sólidas ou viscosas (swarming), o qual participam flagelos laterais. A fim de avaliar a contribuição de ambos os flagelos no contexto da formação de biofilme em superfície plástica e aderência à linhagem celular HEp-2, foram estudadas 76 cepas de A. caviae isoladas de diferentes origens. Os resultados obtidos em nosso estudo demonstraram que a detecção do gene flaA (flagelina polar) foi mais freqüente (94%) que a do gene lafA (flagelina lateral) (71%) e, aparentemente, a presença deste último parece estar condicionada à do primeiro. Todas as cepas que apresentaram o genótipo flaA-lafA-, foram incapazes de formar biofilme, bem como 76% das cepas flaA+lafA-. As cepas provenientes de água foram as que exibiram menor percentual de positividade para o gene da flagelina lateral (57%) e aquelas onde se observou maior incapacidade de formação de biofilme (71%). Além disso, 95% das cepas flaA+lafA+ formaram biofilme e todas as cepas que apresentaram, quantitativamente, um biofilme forte, albergavam ambos os genes. A aderência à HEp-2 se mostrou eficiente em todos os casos onde ao menos um dos flagelos estava presente e em dois casos onde ambos estavam ausentes, com prevalência do padrão agregativo. Em contrapartida, não foi notado uma interferência exclusiva dos flagelos laterais nesse processo. Todas as três cepas que não aderiram ao modelo celular utilizado, ou o fizeram muito discretamente, não exibiram nem o gene flaA, tampouco lafA. Em conclusão aos dados observados, apontamos que uma plena atividade de ambos os flagelos, geralmente, é requerida nos processos de aderência às superfícies abióticas e bióticas. Contudo, trabalhos adicionais sobre a contribuição dessas estruturas na patogênese de A. caviae necessitam ser realizados. / Aeromonas spp. are bacteria Gram-negative able to cause intestinal and extraintestinal diseases. The virulence of some species of this genus has already been associated to several aspects, such as the expression of flagellum and following bacterium mobility. Aeromonas caviae presents two distinct flagellar systems, one of which is responsible for mobility in liquid environments (swimming) at where the polar flagellum is involved, and the other is associated to sliding in solid or viscous surfaces (swarming), in which lateral flagella take part. In order to evaluate the contribution of both flagella in the biofilm formation in plastic surfaces and its adherence to cell line HEp-2, 76 strains of isolated A. caviae from distinct sources were analyzed. The results from our studies showed that detection of gene flaA (polar flagellin) was more frequent (94%) than gene lafA (lateral flagellin) (71%), and apparently, the presence of the last one seems to be conditioned to the first one (the gene flaA). All the strains that presented the genotype flaA-lafA- were unable to form biofilm, such as 76% of strains flaA+lafA-. The aquatic strains were those who showed lesser percentage of positivity for the lateral flagellin gene (57%), and higher incapacity of biofilm formation (71%). Moreover, 95% of the flaA+lafA+ strains formed biofilm, and all strains that quantitatively showed a strong biofilm, contained both genes. The adherence to HEp-2 proved to be efficient in all cases where at least one of the two flagella was present at, and in two cases where both were absent, with prevalence of the aggregative pattern. However, an exclusive interference from the lateral flagella was not perceived in this process. All of the three strains that did not adhere to the cell model used, or that adhered in a very discrete way, did not show neither gene flaA nor gene lafA. In conclusion, we suggest that the complete function of both flagella usually is a requirement in the adherence processes to biotic and abiotic surfaces. However, additional studies on the contribution of these structures in the pathogenesis of A. caviae need to be carried out.

Yes / Here, we present the draft genome sequence of Aeromonas caviae strain L12, which shows quorum-sensing activity. The availability of this genome sequence is important to the research of the quorum-sensing regulatory system in this isolate. / High Impact Research Grants from the University of Malaya (A000001-50001; UM-MOHE HIR Grant UM C/625/1/HIR/MOHE/CHAN/14/1, H-50001-A000027)

Les rejets urbains par temps de pluie dégradent l’état écologique des écosystèmes aquatiques et peuvent induire une exposition des populations humaines aux contaminants chimiques et microbiens (bactéries, virus, parasites). L’objectif de ce travail de thèse était d’évaluer les effectifs et de prédire le devenir de bactéries pathogènes introduites dans les milieux aquatiques par une source majeure comme les eaux usées rejetées par des dispositifs tels que les déversoirs d’orage (DO) et les lagunes d’épuration (WWTL). La répartition d’un agent pathogène fortement liée aux milieux hydriques, Pseudomonas aeruginosa, a été comparée avec celles observées pour des indicateurs de contaminations fécales (E. coli et les entérocoques intestinaux), mais également avec celle de l’espèce pathogène Aeromonas caviae. La dangerosité des formes retrouvées dans ces milieux a été évaluée par approches moléculaires (PFGE et MLST). Les résultats obtenus montrent un fort apport en P. aeruginosa via les eaux usées, avec un effet significatif sur les effectifs observés en fonction de l’intensité des pluies et des périodes de temps sec, et les fluctuations du régime hydrologique et des paramètres physico-chimiques. Une grande diversité infra-spécifique des P. aeruginosa, et la capacité de certains génotypes à s’installer durablement dans ces milieux (macrophytes et périphyton) ont été observées. Certaines souches ont par ailleurs montré une parenté avec des lignées d’infections communautaires, ou encore des clones épidémiques majeurs (PA14 et C). Des études en microcosme ont été effectuées pour valider les interactions observées avec certains macrophytes, et identifier des propriétés d’adhérence bactérienne (dont les lectines) impliquées dans ces interactions. Ces travaux ont impliqué une analyse de la distribution des gènes lecA et lecB, codant des lectines chez P. aeruginosa, et une étude de leurs ligands. Le gène lecA a été localisé dans une zone de forte plasticité génomique. Ces travaux ont permis la description d’une nouvelle structure de l’adhésine LecB / Urban wet-weather discharges degrade the ecological status of aquatic ecosystems and may expose human populations to chemical and microbial contaminants (bacteria, viruses, parasites). The aim of this thesis was to evaluate the numbers and predict the fate of pathogenic bacteria introduced into aquatic ecosystems by a major source like wastewater from devices such as combined sewer overflows (CSO) and wastewater treatment lagoons (WWTL). The distribution of a human pathogen closely linked to hydric environments, Pseudomonas aeruginosa, was compared with those observed for fecal indicators (E. coli and intestinal enterococci), but also with that of Aeromonas caviae pathogenic species. Dangerousness of strains found in these environments was evaluated by molecular approaches (PFGE and MLST). Obtained results showed a high contribution of wastewater in P. aeruginosa release, with a significant effect of rainfall intensity and preceding dry periods, in addition to changes in hydrological regime and physico-chemical parameters on recorded data. A large infra-specific diversity was observed within P. aeruginosa and the ability of some genotypes to colonize permanently aquatic surfaces (macrophytes and periphyton) were observed. Some strains showed a kinship with lineages of community infections or major epidemic clones (PA14 and C). Microcosm studies were performed to validate observed interactions with macrophytes, and to identify bacterialadhesion properties (including lectins) involved in these interactions. These investigations involved analysis of the distribution of lectin encoding loci lecA and lecB within P. aeruginosa, and a study of their ligands. lecA was located in a highly unstable genomic region. This work allowed the description of a new structure of the adhesin LecB