Publications by authors named "Gaetan Thilliez"

The ability of virulent bacteriophages to lyse bacteria influences bacterial evolution, fitness, and population structure. Knowledge of both host susceptibility and resistance factors is crucial for the successful application of bacteriophages as biological control agents in clinical therapy, food processing, and agriculture. In this study, we isolated 12 bacteriophages termed SPLA phage which infect the foodborne pathogen .

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Background: The continued emergence of Salmonella enterica serovar Typhi, with ever increasing antimicrobial resistance, necessitates the use of vaccines in endemic countries. A typhoid fever outbreak in Harare, Zimbabwe, in 2018 from a multidrug resistant S Typhi with additional resistance to ciprofloxacin was the catalyst for the introduction of a typhoid conjugate vaccine programme. We aimed to investigate the emergence and evolution of antimicrobial resistance of endemic S Typhi in Zimbabwe and to determine the population structure, gene flux, and sequence polymorphisms of strains isolated before a typhoid conjugate vaccine programme to provide a baseline for future evaluation of the effect of the vaccination programme.

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Bacteriophages (phages) within the genus are T7-like podoviruses belonging to the subfamily , within the family and have a highly conserved genome organisation. The genomes of these phages range from 37 to 42 kb in size, encode 50-60 genes and are characterised by the presence of direct terminal repeats (DTRs) flanking the linear chromosome. These DTRs are often deleted during short-read-only and hybrid assemblies.

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Introduction: Extended spectrum beta-lactamase (ESBL) producing have become widespread among food producing animals. These strains serve as a reservoir of antibiotic resistance genes (ARGs) and act as a possible source of infection to humans as transmission can occur by direct or indirect contact.

Methods: This study investigated the faecal carriage of ESBL producing and colistin resistant in poultry over a 2-year period (2017-2019) from Zimbabwe.

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Single-cell DNA sequencing has the potential to reveal detailed hierarchical structures in evolving populations of cells. Single cell approaches are increasingly used to study clonal evolution in human ageing and cancer but have not yet been deployed to study evolving clonal microbial populations. Here, we present an approach for single bacterial genomic analysis for evolution experiments using FACS isolation of individual bacteria followed by whole-genome amplification and sequencing.

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Article Synopsis
  • A lot of money has been spent on studying the COVID-19 virus in Africa, leading to over 100,000 virus samples being analyzed to understand the spread of the disease.
  • *More countries in Africa are now able to do these studies themselves, which helps them get results faster and keep a close watch on the virus.
  • *To keep fighting COVID and other diseases, more funding and support for testing and research in Africa is really important for the future.
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This study was designed to characterize extended-spectrum beta-lactamase (ESBL)-producing extra-intestinal pathogenic Escherichia coli (E.coli) (ExPEC) associated with urinary tract infections in nine different geographic regions of Zimbabwe over a 2-year period (2017-2019). A total of 48 ESBL-positive isolates from urine specimen were selected for whole-genome sequencing from 1246 Escherichia coli isolates biobanked at the National Microbiology Reference laboratory using phenotypic susceptibility testing results from the National Escherichia coli Surveillance Programme to provide representation of different geographical regions and year of isolation.

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Article Synopsis
  • Whole genome sequencing was utilized in Zimbabwe to analyze the SARS-CoV-2 outbreak and assess the effectiveness of public health measures between March and October 2020.* ! -
  • Out of 92,299 collected samples, 8099 tested positive for COVID-19, with 156 suitable for sequencing; the data revealed 26 independent virus introductions linked to 12 global variants, predominantly from outside Zimbabwe.* ! -
  • The study highlighted that initial public health measures successfully delayed community transmission of the virus, underscoring the importance of global sequencing data to track and manage the spread effectively.* !
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Article Synopsis
  • The SARS-CoV-2 pandemic in Africa has varied significantly across countries, and its overall impact remains unclear.
  • An analysis of 8,746 genomes from 33 African countries indicated that most outbreaks originated from Europe before international travel restrictions took effect.
  • As the pandemic continued, increased movement and local transmission led to the emergence of several variants within Africa, emphasizing the need for a strong pandemic response on the continent to prevent becoming a source of new variants.
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The emergence of new bacterial pathogens is a continuing challenge for agriculture and food safety. Salmonella Typhimurium is a major cause of foodborne illness worldwide, with pigs a major zoonotic reservoir. Two phylogenetically distinct variants, U288 and ST34, emerged in UK pigs around the same time but present different risk to food safety.

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Background: Typhoid fever, caused by S. enterica ser. Typhi, continues to be a substantial health burden in developing countries.

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Article Synopsis
  • Salmonella enterica variants show diverse adaptations to different hosts, affecting infection outcomes and food safety risks, with a focus on S. Derby subtypes found in humans and swine.* -
  • Certain S. Derby isolates are under-represented in humans and display a unique PFGE profile, indicating specific adaptations to swine and reduced invasion capabilities in human cells.* -
  • A key missense mutation in the hilD gene, crucial for Salmonella's virulence, leads to a loss of function affecting human epithelial cell invasion, while the impact on swine cells is less pronounced, suggesting different invasion strategies for various hosts.*
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Epidemic and pandemic clones of bacterial pathogens with distinct characteristics continually emerge, replacing those previously dominant through mechanisms that remain poorly characterized. Here, whole-genome-sequencing-powered epidemiology linked horizontal transfer of a virulence gene, , to the emergence and clonal expansion of a new epidemic serovar Typhimurium (. Typhimurium) clone.

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Article Synopsis
  • Increased contact between humans and non-human primates poses risks for pathogen transfer and antimicrobial resistance, requiring investigation of their genomic diversity.
  • Researchers sequenced 101 isolates from four non-human primate species in The Gambia, identifying 43 different sequence types, with most simian isolates found in a phylogroup linked to human infections.
  • A low level of antimicrobial resistance was observed, but some simian isolates showed genetic similarities to human clinical cases, highlighting potential recent exchanges between species and the need for monitoring in light of increasing interactions.
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Salmonella enterica serotype Typhimurium (S. Typhimurium) is a leading cause of gastroenteritis and bacteraemia worldwide, and a model organism for the study of host-pathogen interactions. Two S.

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A multi drug resistant 4,[5],12:i- of sequence type 34 (monophasic . Typhimurium ST34) is a current pandemic clone associated with livestock, particularly pigs, and numerous outbreaks in the human population. A large genomic island, termed SGI-4, is present in the monophasic Typhimurium ST34 clade and absent from other .

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Oomycetes such as the potato blight pathogen Phytophthora infestans deliver RXLR effectors into plant cells to manipulate host processes and promote disease. Knowledge of where they localize inside host cells is important in understanding their function. Fifty-two P.

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Physiological races of the oomycete Albugo candida are biotrophic pathogens of diverse plant species, primarily the Brassicaceae, and cause infections that suppress host immunity to other pathogens. However, A. candida race diversity and the consequences of host immunosuppression are poorly understood in the field.

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The oomycete pathogens Phytophthora infestans and P. capsici cause significant crop losses world-wide, threatening food security. In each case, pathogenicity factors, called RXLR effectors, contribute to virulence.

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With the increasing availability of plant pathogen genomes, secreted proteins that aid infection (effectors) have emerged as key factors that help to govern plant-microbe interactions. The conserved CRN (CRinkling and Necrosis) effector family was first described in oomycetes by their capacity to induce host cell death. Despite recent advances towards the elucidation of CRN virulence functions, the relevance of CRN-induced cell death remains unclear.

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Plant associated microbes rely on secreted virulence factors (effectors) to modulate host immunity and ensure progressive infection. Amongst the secreted protein repertoires defined and studied in pathogens to date, the CRNs (for CRinkling and Necrosis) have emerged as one of only a few highly conserved protein families, spread across several kingdoms. CRN proteins were first identified in plant pathogenic oomycetes where they were found to be modular factors that are secreted and translocated inside host cells by means of a conserved N-terminal domain.

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The greatest threat to potato production world-wide is late blight, caused by the oomycete pathogen Phytophthora infestans. A screen of 126 wild diploid Solanum accessions from the Commonwealth Potato Collection (CPC) with P. infestans isolates belonging to the genotype 13-A2 identified resistances in the species S.

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In nature, most plants are resistant to a wide range of phytopathogens. However, mechanisms contributing to this so-called nonhost resistance (NHR) are poorly understood. Besides constitutive defenses, plants have developed two layers of inducible defense systems.

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