Contribution of the Twin-Arginine Translocation System to the Intracellular Survival of Salmonella Typhimurium in Dictyostelium discoideum

The twin-arginine translocation (Tat) system is a specialized secretion pathway required for bacteria to export fully folded proteins through the cytoplasmic membrane. This system is crucial during Salmonella infection of animal hosts. In this study, we show that Salmonella enterica serovar Typhimurium (S. Typhimurium) requires the Tat system to survive and proliferate intracellularly in the social amoeba Dictyostelium discoideum. To achieve this, we developed a new infection assay to assess intracellular bacterial loads in amoeba by direct enumeration of colony forming units (CFU) at different times of infection. Using this assay we observed that a ΔtatABC mutant was internalized in higher numbers than the wild type, and was defective for intracellular survival in the amoeba at all times post infection evaluated. In addition, we assessed the effect of the ΔtatABC mutant in the social development of D. discoideum. In contrast to the wild-type strain, we observed that the mutant was unable to delay the social development of the amoeba at 2 days of co-incubation. This phenotype correlated with defects in intracellular proliferation presented by the ΔtatABC mutant in D. discoideum after 24 h of infection. All phenotypes described for the mutant were reverted by the presence of a plasmid carrying tatABC genes, indicating that abrogation of Tat system attenuates S. Typhimurium in this model organism. Overall, our results indicate that the Tat system is crucial for S. Typhimurium to survive and proliferate intracellularly in D. discoideum and for virulence in this host. To the best of our knowledge, this is the first report on the relevance of the Tat system in the interaction of any bacterial pathogen with the social amoeba D. discoideum

Vaginal infections in a family health clinic in the metropolitan region, chile Infecciones vaginales en un Centro de Salud Familiar de la Región Metropolitana, Chile

© 2015, Sociedad Chilena de Infectologia. All rights reserved. Background: Vaginal infections are a frequent cause for consultation, but their prevalence and etiology vary in different populations. Objectives: To determine the prevalence and etiologies of vaginal infection in women attending a family health center in the Metropolitan Region of Chile. Methods: The microbiological diagnosis was made by wet mount and Gram stain. Diagnosis of trichomoniasis was performed by wet mount, culture and polymerase chain reaction. Results: 101 women aged 15-54, not selected by signs or symptoms of vaginal infection, 46 of them pregnant were included. In 47 women (46.5%), vaginal infections were diagnosed. An association was observed between age and frequency of vaginal infection. The proportion of infections among pregnant and non-pregnant women was similar. The most frequent infections were bacterial vaginosis (16.8%), vulvovaginal candidiasis (11.9%) and co-infections (6.9%). We found 5.9% of i

Vaginal infections in a Family Health Clinic in the Metropolitan Region, Chile

Artículo de publicación ISIBackground: Vaginal infections are a frequent cause for consultation, but their prevalence and etiology vary in different populations. Objectives: To determine the prevalence and etiologies of vaginal infection in women attending a family health center in the Metropolitan Region of Chile. Methods: The microbiological diagnosis was made by wet mount and Gram stain. Diagnosis of trichomoniasis was performed by wet mount, culture and polymerase chain reaction. Results: 101 women aged 15-54, not selected by signs or symptoms of vaginal infection, 46 of them pregnant were included. In 47 women (46.5%), vaginal infections were diagnosed. An association was observed between age and frequency of vaginal infection. The proportion of infections among pregnant and non-pregnant women was similar. The most frequent infections were bacterial vaginosis (16.8%), vulvovaginal candidiasis (11.9%) and co-infections (6.9%). We found 5.9% of intermediate microbiota cases, 3% of trichomoniasis and 2% of aerobic vaginitis. Symptoms of vaginal infection had poor agreement with microbiological findings. Otherwise physical signs had good agreement with the presence of infection, but low to moderate concordance with a specific etiology. Conclusions: We found a high prevalence of vaginal infections in the study population. It is necessary to improve the definitions and criteria of microbiological diagnosis of co-infections and intermediate microbiota, for them to be diagnosed in the clinical practice. More descriptive questionnaires are recommended to enhance the usefulness of clinical examination.Introducción: Las infección vaginales constituyen un motivo frecuente de consulta, pero su prevalencia y etiología varían en distintas poblaciones. Objetivos: Determinar la prevalencia y tipos de infección vaginal en mujeres atendidas en un centro de salud familiar de la Región Metropolitana. Métodos: El diagnóstico microbiológico fue efectuado mediante examen microscópico al fresco y tinción de Gram y para tricomoniasis examen al fresco, cultivo y reacción de la polimerasa en cadena. Resultados: Se incluyeron 101 mujeres de 15-54 años, no seleccionadas por signos ó síntomas, 46 de ellas embarazadas. En 47 mujeres (46,5%) se diagnosticaron infecciones vaginales. Se observó asociación entre edad y frecuencia de infección vaginal. La proporción de infecciones entre gestantes y no gestantes fue similar. Las infecciones más frecuentes fueron vaginosis bacteriana (16,8%), candidiasis vulvo-vaginal (11,9%) y co-infecciones (6,9%). Se observó 5,9% casos de microbiota intermedia, 3% de tricomoniasis y 2% de vaginitis aeróbica. Los síntomas de infección vaginal tuvieron mala concordancia con los hallazgos microbiológicos. A su vez, los signos físicos tuvieron buena concordancia con la existencia de infección, pero escasa a moderada concordancia con una etiología específica. Conclusiones: Se encontró alta frecuencia de infecciones vaginales. Es necesario mejorar las definiciones y criterios de diagnóstico microbiológico de las co-infecciones y microbiota intermedia, para ser diagnosticadas en la práctica clínica. Se recomienda emplear cuestionarios más descriptivos para mejorar la utilidad del examen clínico.Proyecto FONIS SA12I224

Relevant genes linked to virulence are required for Salmonella Typhimurium to survive intracellularly in the social amoeba Dictyostelium discoideum

The social amoeba Dictyostelium discoideum has proven to be a useful model for studying relevant aspects of the host-pathogen interaction. In this work, D. discoideum was used as a model to study the ability of S. Typhimurium to survive in amoebae and to evaluate the contribution of selected genes in this process. To do this, we performed infection assays using axenic cultures of D. discoideum co-cultured with wild-type S. Typhimurium and/or defined mutant strains. Our results confirmed that wild-type S. Typhimurium is able to survive intracellularly in D. discoideum. In contrast, mutants ΔaroA and ΔwaaL are defective in intracellular survival in this amoeba. Next, we included in our study a group of mutants in genes directly linked to Salmonella virulence. Of note, mutants ΔinvA, ΔssaD, ΔclpV and ΔphoPQ also showed an impaired ability to survive intracellularly in D. discoideum. This indicates that S. Typhimurium requires a functional biosynthetic pathway of aromatic compounds, a lipopolysaccharide containing a complete O-antigen, the type III secretion systems (T3SS) encoded in SPI-1 and SPI-2, the type VI secretion system (T6SS) encoded in SPI-6 and PhoP/PhoQ two-component system to survive in D. discoideum. To our knowledge, this is the first report on the requirement of O-antigen and T6SS in the survival of Salmonella within amoebae. In addition, mutants ΔinvA and ΔssaD were internalized in higher numbers than the wild-type strain during competitive infections, suggesting that S. Typhimurium requires the T3SS encoded in SPI-1 and SPI-2 to evade phagocytosis by D. discoideum. Altogether, these results indicate that S. Typhimurium exploits a common set of genes and molecular mechanisms to survive within amoeba and animal host cells. The use of D. discoideum as a model for host-pathogen interactions will allow us to discover the gene repertoire used by Salmonella to survive inside the amoeba and to study the cellular processes that are affected during infection