RESUMO
Gram-negative bacteria from the Legionella genus are intracellular pathogens that cause a severe form of pneumonia called Legionnaires' disease. The bacteria replicate intracellularly in macrophages, and the restriction of bacterial replication by these cells is critical for host resistance. The activation of the NAIP5/NLRC4 inflammasome, which is readily triggered in response to bacterial flagellin, is essential for the restriction of bacterial replication in murine macrophages. Once activated, this inflammasome induces pore formation and pyroptosis and facilitates the restriction of bacterial replication in macrophages. Because investigations related to the NLRC4-mediated restriction of Legionella replication were performed using mice double deficient for caspase-1 and caspase-11, we assessed the participation of caspase-1 and caspase-11 in the functions of the NLRC4 inflammasome and the restriction of Legionella replication in macrophages and in vivo. By using several species of Legionella and mice singly deficient for caspase-1 or caspase-11, we demonstrated that caspase-1 but not caspase-11 was required for pore formation, pyroptosis, and restriction of Legionella replication in macrophages and in vivo. By generating F1 mice in a mixed 129 × C57BL/6 background deficient (129 × Casp-11(-/-) ) or sufficient (129 × C57BL/6) for caspase-11 expression, we found that caspase-11 was dispensable for the restriction of Legionella pneumophila replication in macrophages and in vivo. Thus, although caspase-11 participates in flagellin-independent noncanonical activation of the NLRP3 inflammasome, it is dispensable for the activities of the NLRC4 inflammasome. In contrast, functional caspase-1 is necessary and sufficient to trigger flagellin/NLRC4-mediated restriction of Legionella spp. infection in macrophages and in vivo.
Assuntos
Proteínas Reguladoras de Apoptose/imunologia , Proteínas de Ligação ao Cálcio/imunologia , Caspase 1/imunologia , Caspases/imunologia , Legionella/imunologia , Doença dos Legionários/imunologia , Macrófagos/imunologia , Piroptose/imunologia , Animais , Proteínas Reguladoras de Apoptose/genética , Proteínas Reguladoras de Apoptose/metabolismo , Western Blotting , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Caspase 1/genética , Caspase 1/metabolismo , Caspases/genética , Caspases/metabolismo , Caspases Iniciadoras , Linhagem Celular , Células Cultivadas , Ativação Enzimática/imunologia , Flagelos/imunologia , Interações Hospedeiro-Patógeno/imunologia , Interleucina-1beta/biossíntese , Interleucina-1beta/imunologia , Legionella/classificação , Legionella/fisiologia , Legionella pneumophila/imunologia , Legionella pneumophila/fisiologia , Doença dos Legionários/genética , Doença dos Legionários/microbiologia , Macrófagos/metabolismo , Macrófagos/microbiologia , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microscopia de Fluorescência , Piroptose/genética , Especificidade da EspécieRESUMO
Legionellaceae is a family of gram-negative, mesophilic, and facultative intracellular parasitic bacteria that inhabits freshwater environments. In this article, the Legionella population of water samples from the North and South Lake, located close to the Brazilian Scientific Station on King George Island, Keller Peninsula, Antarctica has been characterized. Culture onto selective medium and a independent-culture method were applied to the samples. In our attempt to isolate Legionella species from Antarctic lakes, we were able to obtain one L. pneumophila colony by an amoebic coculture procedure followed by plate culture onto a selective medium. In addition, results obtained from phylogenetic inference showed the presence of noncharacterized specimens of Legionella spp. These findings indicated the presence of legionellae in Antarctica and suggest that these bacteria can adapt to extreme conditions and open new possibilities for understanding the survival strategies of mesophilic Legionellaceae living in Antarctic environments. Furthermore, the isolation of these symbiotic bacteria in Antarctic lakes will allow future studies on cold-resistant mechanisms of legionellae in polar environments.
Assuntos
Biodiversidade , Água Doce/microbiologia , Legionellaceae , Regiões Antárticas , Clonagem Molecular , Meios de Cultura , DNA Bacteriano/análise , DNA Bacteriano/isolamento & purificação , Ecossistema , Genes de RNAr , Legionella/classificação , Legionella/genética , Legionella/isolamento & purificação , Legionellaceae/classificação , Legionellaceae/genética , Legionellaceae/isolamento & purificação , Dados de Sequência Molecular , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
Legionella species are ubiquitous bacteria in aquatic environments. To examine the effect of anthropogenic impacts and physicochemical characteristics on the Legionellaceae population, we collected water from two sites in the Itanhaém River system in the Atlantic Forest of Brazil. One sample was collected from an upstream pristine region, the other from a downstream estuarine region moderately affected by untreated domestic sewage. Cultures on a selective medium failed to isolate Legionella species. Culture-independent methods showed that water from the estuarine aquatic habitat contained DNA sequences homologous to the 16S ribosomal DNA gene of Legionella pneumophila and non-pneumophila species. In pristine water, only two sequences related to L. pneumophila were detected. The results suggest that salinity and anthropogenic factors, such as wastewater discharge, favor a diversity of Legionella species, whereas pristine freshwater selects for Legionella pneumophila.
Assuntos
Ecossistema , Água Doce/microbiologia , Legionella/classificação , Microbiologia da Água , Biodiversidade , Brasil , Legionella/genética , Legionella/crescimento & desenvolvimento , Filogenia , Árvores , Clima Tropical , Poluição da ÁguaRESUMO
Se estudiaron 11 muestras clínicas y 5 ambientales en busca de microorganismos del género Legionella en el curso de una investigación realizada para esclarecer las causas de sepsis respiratorias en un servicio de cirugía cardiovascular pediátrica. Dos de las últimas resultaron positivas, en 1 de las cuales se aisló Legionella bozemanii, éste constituye el primer reporte en nuestro país. Aunque no se pudo demostrar relación entre los cuadros respiratorios y el hallazgo, fue importante conocer la existencia de este gemen pues es frecuente en el medio hospitalario y es causante de un número importante de infecciones nosocomiales con un alto costo de vidas y recursos
Assuntos
Humanos , Legionella/classificação , Legionella/isolamento & purificação , Transtornos Respiratórios/microbiologia , Centro Cirúrgico Hospitalar , Cirurgia Torácica , CubaRESUMO
Este trabajo compendia la información de la familia Legionellaceae desde su descubrimiento y clasificación, hasta los últimos datos obtenidos de investigaciones que sobre el microorganismo se han desarrollado. Legionella forma parte de ecosistemas acuáticos, requiere de L-cisteína y hierro para su desarrollo in vitro. Produce enfermedad por invasión de tejido local; elaboración de toxinas; liberación de endotoxinas asociadas a la pared celular; mecanismos inmunológicos; o, combinación de estos factores. Fundamentalmente produce dos entidades clínicas; "fiebre Pontiac" y "enfermedad de los legionarios". La neumonía por Legionella se presenta sobre todo en personas con mecanismos de defensa alterados o con enfermedades predisponentes como el alcoholismo, por lo que en los hospitales debe tenerse cuidado especial a pacientes de alto riesgo en unidades de trasplante o con terapéutica inmunosupresora. Se considera a la legionelosis como enfermedad ocupacional o de viajeros y el tratamiento de elección es con eritromicina