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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 20 January 2015, Vol.112(3), pp.863-8
    Description: Many bacterial pathogens are specialized, infecting one or few hosts, and this is often associated with more acute disease presentation. Specific genomes show markers of this specialization, which often reflect a balance between gene acquisition and functional gene loss. Within Salmonella enterica subspecies enterica, a single lineage exists that includes human and animal pathogens adapted to cause infection in different hosts, including S. enterica serovar Enteritidis (multiple hosts), S. Gallinarum (birds), and S. Dublin (cattle). This provides an excellent evolutionary context in which differences between these pathogen genomes can be related to host range. Genome sequences were obtained from ∼ 60 isolates selected to represent the known diversity of this lineage. Examination and comparison of the clades within the phylogeny of this lineage revealed signs of host restriction as well as evolutionary events that mark a path to host generalism. We have identified the nature and order of events for both evolutionary trajectories. The impact of functional gene loss was predicted based upon position within metabolic pathways and confirmed with phenotyping assays. The structure of S. Enteritidis is more complex than previously known, as a second clade of S. Enteritidis was revealed that is distinct from those commonly seen to cause disease in humans or animals, and that is more closely related to S. Gallinarum. Isolates from this second clade were tested in a chick model of infection and exhibited a reduced colonization phenotype, which we postulate represents an intermediate stage in pathogen-host adaptation.
    Keywords: Salmonella ; Host Adaptation ; Metabolism ; Pseudogene ; Adaptation, Physiological ; Evolution, Molecular ; Genome, Bacterial ; Salmonella -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: The Journal of Bacteriology, 2011, Vol. 193(7), p.1771
    Description: Massively parallel sequencing of transposon-flanking regions assigned the genotype and fitness score to 91% of Escherichia coli O157:H7 mutants previously screened in cattle by signature-tagged mutagenesis (STM). The method obviates the limitations of STM and markedly extended the functional annotation of the prototype E. coli O157:H7 genome without further animal use. doi: 10.1128/JB.01292-10
    Keywords: Transposons -- Physiological Aspects ; Escherichia Coli -- Physiological Aspects ; Escherichia Coli -- Genetic Aspects ; Cattle -- Physiological Aspects ; Cattle -- Genetic Aspects ; Dna Sequencing -- Research;
    ISSN: 0021-9193
    ISSN: 00219193
    E-ISSN: 10985530
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  • 3
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 15 May 2012, Vol.109(20), pp.E1277-86
    Description: More than 50 y of research have provided great insight into the physiology, metabolism, and molecular biology of Salmonella enterica serovar Typhimurium (S. Typhimurium), but important gaps in our knowledge remain. It is clear that a precise choreography of gene expression is required for Salmonella infection, but basic genetic information such as the global locations of transcription start sites (TSSs) has been lacking. We combined three RNA-sequencing techniques and two sequencing platforms to generate a robust picture of transcription in S. Typhimurium. Differential RNA sequencing identified 1,873 TSSs on the chromosome of S. Typhimurium SL1344 and 13% of these TSSs initiated antisense transcripts. Unique findings include the TSSs of the virulence regulators phoP, slyA, and invF. Chromatin immunoprecipitation revealed that RNA polymerase was bound to 70% of the TSSs, and two-thirds of these TSSs were associated with σ(70) (including phoP, slyA, and invF) from which we identified the -10 and -35 motifs of σ(70)-dependent S. Typhimurium gene promoters. Overall, we corrected the location of important genes and discovered 18 times more promoters than identified previously. S. Typhimurium expresses 140 small regulatory RNAs (sRNAs) at early stationary phase, including 60 newly identified sRNAs. Almost half of the experimentally verified sRNAs were found to be unique to the Salmonella genus, and 〈20% were found throughout the Enterobacteriaceae. This description of the transcriptional map of SL1344 advances our understanding of S. Typhimurium, arguably the most important bacterial infection model.
    Keywords: Gene Expression Regulation, Bacterial -- Genetics ; RNA, Small Untranslated -- Genetics ; Regulatory Sequences, Ribonucleic Acid -- Genetics ; Salmonella Typhimurium -- Genetics ; Transcription, Genetic -- Genetics
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 4
    Language: English
    In: The Journal of infectious diseases, 15 February 2009, Vol.199(4), pp.602-3
    Keywords: Global Health ; Salmonella Infections -- Epidemiology ; Salmonella Enterica -- Pathogenicity
    ISSN: 0022-1899
    E-ISSN: 15376613
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  • 5
    Language: English
    In: The Lancet, 08 November 2014, Vol.384(9955), pp.1691-1697
    Description: Shigellosis (previously bacillary dysentery) was the primary diarrhoeal disease of World War 1, but outbreaks still occur in military operations, and shigellosis causes hundreds of thousands of deaths per year in developing nations. We aimed to generate a high-quality reference genome of the historical isolate NCTC1 and to examine the isolate for resistance to antimicrobials. In this genomic analysis, we sequenced the oldest extant serotype 2a isolate using single-molecule real-time (SMRT) sequencing technology. Isolated from a soldier with dysentery from the British forces fighting on the Western Front in World War 1, this bacterium, NCTC1, was the first isolate accessioned into the National Collection of Type Cultures. We created a reference sequence for NCTC1, investigated the isolate for antimicrobial resistance, and undertook comparative genetics with reference strains isolated during the 100 years since World War 1. We discovered that NCTC1 belonged to a 2a lineage of with which it shares common characteristics and a large core genome. NCTC1 was resistant to penicillin and erythromycin, and contained a complement of chromosomal antimicrobial resistance genes similar to that of more recent isolates. Genomic islands gained in the 2a lineage over time were predominately associated with additional antimicrobial resistances, virulence, and serotype conversion. This 2a lineage is a well adapted pathogen that has continued to respond to selective pressures. We have created a valuable historical benchmark for shigellae in the form of a high-quality reference sequence for a publicly available isolate. The Wellcome Trust.
    Keywords: Medicine
    ISSN: 0140-6736
    E-ISSN: 1474-547X
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  • 6
    In: Journal of Antimicrobial Chemotherapy, 2012, Vol. 67(3), pp.589-599
    Description: OBJECTIVES: The initial aim of this study was to use a systems biology approach to analyse a ciprofloxacin-selected multidrug-resistant (MDR) Salmonella enterica serotype Typhimurium, L664.METHODS: The whole genome sequence and transcriptome of L664 were analysed. Site-directed mutagenesis to recreate each mutation was carried out, followed by phenotypic characterization and mutation frequency analysis. As a mutation in the TCA cycle was detected we tested the controversial hypothesis regarding the bacterial response to bactericidal antibiotics, put forward by Kohanski et al. (Cell 2007; 130: 797-810 and Mol Cell 2010; 37: 311-20), that exposure of bacteria to agents such as ciprofloxacin produces reactive oxygen species (ROS), which transiently increase the mutation rate giving rise to MDR bacteria.RESULTS: L664 contained a mutation in ramR that conferred MDR. A mutation in tctA affected the TCA cycle and conferred the inability to grow on minimal agar. The virulence of L664 was not attenuated. Ciprofloxacin exposure produced ROS in L664 and SL1344 (tctA::aph), but it was reduced and occurred later. There were no significant differences in the rates of killing or mutations per generation to antibiotic resistance between the strains.CONCLUSIONS: Whilst we confirm production of ROS in response to ciprofloxacin, we have no data to support the hypothesis that this leads to selection of MDR strains. Our results indicate that the mutations in tctA and glgA were random as they did not pre-exist in the parental strain, and that the mutation in tctA did not provide a survival advantage or disadvantage in the presence of antibiotic.
    Keywords: Tcta ; Ramr ; Efflux Pumps ; Genome Sequences
    ISSN: 0305-7453
    E-ISSN: 1460-2091
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  • 7
    Language: English
    In: Applied and Environmental Microbiology, 2012, Vol. 78(7), p.2147
    Description: The insertion sites of the conjugative transposon Tn916 in the anaerobic pathogen Clostridium difficile were determined using Illumina Solexa high-throughput DNA sequencing of Tn916 insertion libraries in two different clinical isolates: 630ΔE, an erythromycin-sensitive derivative of 630 (ribotype 012), and the ribotype 027 isolate R20291, which was responsible for a severe outbreak of C. difficile disease. A consensus 15-bp Tn916 insertion sequence was identified which was similar in both strains, although an extended consensus sequence was observed in R20291. A search of the C. difficile 630 genome showed that the Tn916 insertion motif was present 100,987 times, with approximately 63,000 of these motifs located in genes and 35,000 in intergenic regions. To test the usefulness of Tn916 as a mutagen, a functional screen allowed the isolation of a mutant. This mutant contained Tn916 inserted into a gene involved in flagellar biosynthesis.
    Keywords: Engineering ; Biology ; Economics;
    ISSN: 1098-5336
    ISSN: 10985336
    ISSN: 00992240
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  • 8
    In: Nature Genetics, 2016
    Description: An epidemiological paradox surrounds Salmonella enterica serovar Enteritidis. In high-income settings, it has been responsible for an epidemic of poultry-associated, self-limiting enterocolitis, whilst in sub-Saharan Africa it is a major cause of invasive nontyphoidal Salmonella disease, associated with high case-fatality. Whole-genome sequence analysis of 675 isolates of S . Enteritidis from 45 countries reveals the existence of a global epidemic clade and two novel clades of S . Enteritidis that are each geographically restricted to distinct regions of Africa. The African isolates display genomic degradation, a novel prophage repertoire and have an expanded, multidrug resistance plasmid. S . Enteritidis is a further example of a Salmonella serotype that displays niche plasticity, with distinct clades that enable it to become a prominent cause of gastroenteritis in association with the industrial production of eggs, and of multidrug resistant, bloodstream invasive infection in Africa.
    Keywords: Article ; Enteritidis ; Global ; Multidrug Resistant ; Bacteraemia ; Gastroenteritis;
    ISSN: 1061-4036
    E-ISSN: 1546-1718
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  • 9
    Language: English
    In: EcoSal Plus, November 2012, Vol.5(1)
    Description: Human salmonellosis is generally associated with Salmonella enterica from subspecies enterica (subspecies I). Acute infections can present in one of four ways: enteric fever, gastroenteritis, bacteremia, or extraintestinal focal infection. As with other infectious diseases, the course and outcome of the infection depend on a variety of factors, including the infecting organism, the inoculating dose, and the immune status and genetic background of the host. For serovarsTyphi and Paratyphi A there is a clear association between the genetic background of the serovar and systemic infection in humans. For serovars Paratyphi B and Paratyphi C, a good clinical description of the host and detailed population genetics of the pathogen are necessary before more detailed genetic studies of novel virulence factors,or host factors,can be initiated. For the nontyphoidalserovars (NTS) the situation is less clear. Serovars Typhimurium and Enteritidis are the most common within the food chain, and so the large number of invasive infections associated with these serovars is most likely due to exposure rather than to increased virulence of the pathogen. In Africa, however, a closely related group of strains of serovar Typhimurium, associated with HIV infection, may have become host adapted tohumans, suggesting that not all isolates called "Typhimurium" should be considered as a single group. Here we review current knowledge of the salmonellae for which invasive disease in humans is an important aspect of their population biology.
    ISSN: 2324-6200
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  • 10
    Language: English
    In: Journal of infection in developing countries, 05 September 2017, Vol.11(8), pp.583-590
    Description: Non-typhoidal Salmonella (NTS) represents a leading cause of food-borne disease worldwide. It is a global public health concern: more than 94 million cases and 115,000 deaths are reported every year, with a disproportionate impact in developing countries. The prevalence of multi-drug-resistant (MDR) Salmonella strains is another major health concern which affects antimicrobial treatment, as many studies report that infections caused by MDR strains are more severe than those caused by susceptible strains. In Algeria, NTS represent one of the primary causes of salmonellosis in both humans and food animal production, especially poultry. Epidemiological surveillance systems and monitoring programs for Salmonella infections are essential requirements to provide data useful for the effective detection and control of Salmonella outbreaks. The present review will supply a perspective on NTS infection, pathogenesis and antimicrobial resistance with a focus on the epidemiology of salmonellosis in Algeria.
    Keywords: Public Health;
    ISSN: 20366590
    E-ISSN: 1972-2680
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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