Extensive in vivo resilience of persistent Salmonella

Chronic infections caused by persistent pathogens represent an important health problem. Here, we establish a simple practical mouse Salmonella infection model for identifying bacterial maintenance functions that are essential for persistency. In this model, a substantial fraction of Salmonella survived even several days of treatment with a potent fluoroquinolone antibiotic indicating stringency of the model. Evaluation of twelve metabolic defects revealed dramatically different requirements for Salmonella during persistency as compared to acute infections. Disrupted synthesis of unsaturated/cyclopropane fatty acids was the only defect that resulted in rapid Salmonella clearance suggesting that this pathway might contain suitable targets for antimicrobial chemotherapy of chronic infection

Functional Characterization of the Incomplete Phosphotransferase System (PTS) of the Intracellular Pathogen Brucella melitensis

Background: In many bacteria, the phosphotransferase system (PTS) is a key player in the regulation of the assimilation of alternative carbon sources notably through catabolic repression. The intracellular pathogens Brucella spp. possess four PTS proteins (EI Ntr, NPr, EIIA Ntr and an EIIA of the mannose family) but no PTS permease suggesting that this PTS might serve only regulatory functions

The central metabolism regulator EIIAGlc switches Salmonella from growth arrest to acute virulence through activation of virulence factor secretion

The ability of Salmonella to cause disease depends on metabolic activities and virulence factors. Here, we show that a key metabolic protein, EIIAGlc, is absolutely essential for acute infection, but not for Salmonella survival, in a mouse typhoid fever model. Surprisingly, phosphorylation-dependent EIIAGlc functions, including carbohydrate transport and activation of adenylate cyclase for global regulation, do not explain this virulence phenotype. Instead, biochemical studies, in vitro secretion and translocation assays, and in vivo genetic epistasis experiments suggest that EIIAGlc binds to the type three secretion system 2 (TTSS-2) involved in systemic virulence, stabilizes its cytoplasmic part including the crucial TTSS-2 ATPase, and activates virulence factor secretion. This unexpected role of EIIAGlc reveals a striking direct link between central Salmonella metabolism and a crucial virulence mechanism

Artificial signaling in mammalian cells enabled by prokaryotic two-component system

ISSN:1552-4450ISSN:1552-446

Isolation and Characterization of Bile Salts-Sensitive Mutants of Enterococcus faecalis

International audienceA library of insertional mutants of Enterococcus faecalis was constructed; it allowed the isolation and the characterization of 10 mutants affected in resistance to bile salts. Insertion loci of two mutants corresponded to genes of unknown function, while the amino acid sequences deduced from the other loci were homologous to proteins related to DNA repair, oxidative response, transcriptional regulation, dGTP hydrolysis, membrane composition, or cell wall synthesis. Further characterization of one mutant revealed that the insertion within the E. faecalis sagA gene led to a decrease of the resistance towards numerous independent physicochemical stresses, to modifications of the cell wall integrity, and to perturbations of cell division with septation anomalies

Cloning and characterization of a gene encoding a cold-shock protein in Lactobacillus casei.

One csp-like gene, called cspA, from the lactic acid bacterium Lactobacillus casei was identified by an inverse polymerase chain reaction approach based on degenerate primers. cspA encodes a protein of 66 amino acid residues, which displays at least 74% identity with Csp proteins of Lactobacillus genera. Northern blot analysis revealed that cspA is transcribed monocistronically and that its expression is induced after a temperature downshift from 37 degrees C to 20 degrees C. The transcriptional start site has been determined and is situated 98 bp upstream of the initiation codon. A cspA mutant strain was constructed and it showed reduced growth rate compared with the wild type at both optimal and low temperatures, demonstrating that CspA plays an important role in the physiology of L. casei

Colonization kinetics of <i>Salmonella enterica serovar Typhimurium purA ssaGH</i> in systemically infected BALB/c mice.

<p>Data are shown for spleen (<b>A</b>) and liver (<b>B</b>) of individual untreated mice (open circles), and mice that were treated from day two post infection with enrofloxacin (filled circles). Statistical significance of clearance at day 6 compared to day 4 were determined by t-test of log-transformed data (**, <i>P</i><0.01; n.s., not significant).</p

Colonization kinetics of four compromised mutants in spleen (open circles) and liver (filled circles).

<p>Small residual colonization levels after seven days of infection suggested that all shown genes contributed to <i>Salmonella</i> survival but were not absolutely essential. Statistical significance of clearance at day 7 compared to day 1 in spleen was determined by t-test of log-transformed data (***, <i>P</i><0.001).</p

Clearance of <i>Salmonella purA ssaGH fabB</i> from infected mice.

<p>A) Colonization kinetics in spleen (open circles) and liver (filled circles). Similar results were obtained in three independent experiments. Statistical significance of clearance at day 7 compared to day 1 were determined by t-test of log-transformed data (***, <i>P</i><0.001; **, <i>P</i><0.01; *, <i>P</i><0.05; n.s., not significant). B) Heterogeneity of colony size on agar plates. Similar data were obtained for two independent in vitro cultures and five independent ex vivo cultures.</p