Jean-Pierre Ernest Clément Hernalsteens

Vrije Universiteit Brussel | VUB · Department of Biology

The endogenous plasmid pUTI89 harbored by the uropathogenic Escherichia coli (UPEC) strain UTI89 plays an important role in the acute stage of infection. The partitioning gene parB is important for stable inheritance of pUTI89. However, the function of partitioning genes located on the plasmid in pathogenesis of UPEC still needs to be further inves...

Background: Methicillin-resistant Staphylococcus aureus (MRSA), a leading cause of chronic infections, forms prolific biofilms which afford an escape route from antibiotic treatment and host immunity. However, MRSA clones are genetically diverse, and mechanisms underlying biofilm formation remain under-studied. Such studies form the basis for devel...

Almost 40 years ago the first transgenic plant was generated through Agrobacterium tumefaciens-mediated transformation, which, until now, remains the method of choice for gene delivery into plants. Ever since, optimized Agrobacterium strains have been developed with additional (genetic) modifications that were mostly aimed at enhancing the transfor...

The phAPEC6 genome encodes 551 predicted gene products, with the vast majority (83%) of unknown function. Of these, 62 have been identified as virion-associated proteins by mass spectrometry (ESI-MS/MS), including the major capsid protein (Gp225; present in 1620 copies), which shows a HK97 capsid protein-based fold. Cryo-electron microscopy experim...

In methicillin-sensitive Staphylococcus aureus (MSSA), the tricarboxylic acid (TCA) cycle is known to negatively regulate production of the major biofilm-matrix exopolysaccharide, PIA/PNAG. However, methicillin-resistant S. aureus (MRSA) produce a primarily proteinaceous biofilm matrix, and contribution of the TCA-cycle therein remains unclear. Uti...

Campylobacteriosis is a widespread infectious disease, leading to a major health and economic burden. Chickens are considered as the most common infection source for humans. Campylobacter mainly multiplies in the mucus layer of their caeca. No effective control measures are currently available, but passive immunisation of chickens with pathogen-spe...

Purification of flagellin of the C. jejuni strain KC40 flagella. (PDF)

Immunofluorescence microscopy confirms the interaction of Nb5 and Nb23 with Campylobacter isolates. (A, B, C) C. jejuni strain KC40, (D, E, F) C. jejuni strain Cam12/0156 and (G, H, I) C. coli strain K43/5. The binding of Nb5 is shown in A, D and G and the binding of Nb23 in B, E and H. As a negative control, the fluorescently labelled (C, F, I) V1...

Expression of chimeric antibodies in seeds of homozygous and heterozygous plants. ELISA was used for the analysis of seed extracts from A. thaliana plants transformed with (A) Nb23-IgA constructs and (B) Nb23-IgY constructs. The results of the extracts of the homozygous plants are visualised by the histogram with hatched shading. Extract of wild-ty...

ELISA for the confirmation of the interaction of anti-flagellin nanobodies with (A) purified flagellins and (B) C. jejuni KC40. Bound His-tagged nanobodies were detected with mouse anti-histidine monoclonal antibodies and goat anti-mouse IgG. The error bars correspond to the standard deviation. (TIF)

Determination of the chimeric antibody concentration in extracts of A. thaliana seeds with the Chicken IgA ELISA Kit. (PDF)

Construction of the synthetic Nb-IgY or Nb-IgA fusion genes. (PDF)

Phage library construction and selection of anti‑flagellin Campylobacter nanobodies. (PDF)

Thermal and pH stability of nanobodies. (PDF)

Campylobacter infections are among the most prevalent foodborne infections in humans, resulting in a massive disease burden worldwide. Broilers have been identified as the major source of campylobacteriosis and reducing Campylobacter loads in the broiler caeca has been proposed as an effective measure to decrease the number of infections in humans....

Host-defense peptides and proteins are vital for first line protection against bacteria. Most host-defense peptides and proteins common in vertebrates have been studied primarily in mammals, while their orthologues in non-mammalian vertebrates received less attention. We found that the European Common Frog Rana temporaria expresses a protein in its...

Methicillin-resistant Staphylococcus aureus (MRSA)-USA300 is notorious for its ability to cause community- and healthcare-acquired infections, which are even more difficult to treat when associated with a biofilm phenotype. We aimed to characterize the genetic determinants of biofilm formation in a USA300 skin abscess isolate (UAS391) that formed p...

To investigate whether plasmid-free cells of pathogenic E. coli can be isolated by disrupting a single gene in an endogenous plasmid without further treatment, the effect of the disruption of partitioning genes on the inheritance of the endogenous plasmid pUTI89 of the uropathogenic E. coli strain UTI89 was studied. We found that mutation of parB,...

Objectives Epidemic methicillin-resistant S. aureus (MRSA) clones cause infections in both hospital and community settings. As a biofilm phenotype further facilitates evasion of the host immune system and antibiotics, we compared the biofilm-forming capacities of various MRSA clones.Methods Seventy-six MRSA classified into 13 clones (USA300, EMRSA-...

Background De novo genome assembly can be challenging due to inherent properties of the reads, even when using current state-of-the-art assembly tools based on de Bruijn graphs. Often users are not bio-informaticians and, in a black box approach, utilise assembly parameters such as contig length and N50 to generate whole genome sequences, potential...

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious infections that are even more difficult to treat when associated with a biofilm phenotype that facilitates evasion of the host immune system and antibiotics. As a first step toward understanding the mechanisms underlying biofilm formation, we sequenced the genomes of two prolific bio...

Bacterial infections in animals impact our food production, leading to economic losses due to food rejection and the need for preventive and curative measures. Since the onset of the antibiotic era, the rise of antibiotic-resistant pathogens is causing scares in health care and food producing facilities worldwide. In the search of new therapeutics,...

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in poultry, leading to important economic losses worldwide. To cure APEC-infected chickens, a cocktail of four different APEC-specific bacteriophages (phages) was composed and tested. Specific phages were selected from a collection of phages isolated in Belgium. The selection was based...

Bacteriophage phAPEC8 is an Escherichia coli-infecting myovirus, isolated on an avian pathogenic Escherichia coli (APEC) strain. APEC strains cause colibacillosis in poultry, resulting in high mortality levels and important economic losses. Genomic analysis of the 147,737-bp double-stranded DNA phAPEC8 genome revealed that 53% of the 269 encoded pr...

NAD and NADP are ubiquitous in the metabolism of Escherichia coli K-12. NAD auxotrophy can be rendered by mutation in any of the three genes nadB, nadA and nadC. The nadB and nadA genes were defined as antivirulence loci in Shigella spp., as a mutation (mainly in nadB) disrupting the synthesis of quinolinate is required for virulence. Uropathogenic...

A number of allele replacement methods can be used to mutate bacterial genes. For instance, the Red recombinase system of phage Lambda has been used very efficiently to inactivate chromosomal genes in E. coli K-12, through recombination between regions of homology. However, this method does not work reproducibly in some clinical E. coli isolates. T...

Surface exposure of antigens on bacterial cells can be critical for eliciting an effective antibody response. Therefore, we investigated the cellular localization of the fimbrial F17a-G receptor-binding domain, fused to the translocator domain of the AIDA-I autotransporter. Synthesis of the fusion protein, under the control of the L-arabinose-induc...

We examined the potential of inactivated Salmonella strains to induce protective antibodies against two adhesins of pathogenic Escherichia coli. The receptor-binding domains of the F17a-G adhesin of F17a fimbriae and of the FimH adhesin of type 1 fimbriae were fused to the translocator domain of the autotransporter AIDA-I. An IgG response against F...

Virulence genes regulated by the SsrA/B system are indispensable for systemic disease in BALB/c mice. The role of this regulating system in the pathogenesis of Salmonella Typhimurium infections in pigs is not documented. In the present study, the interactions of Salmonella Typhimurium and an ssrA/B mutant were compared in vitro and in vivo. The ssr...

Data collection and processing, refinement statistics and model quality. (0.02 MB DOC)

Crystals of the FimH receptor-binding domain in complex with oligomannose-3. The crystals were grown by the vapour diffusion method in 1.0 M Li2SO4, 0.1 M Tris pH 8.5, 0.01 M NiCl2, A, in sitting drop, diffracting to 2.6 {Angstrom} resolution, and B, in hanging drop, optimized by the addition of 3% glycerol to the precipitant and diffracting to a m...

[This corrects the article on p. e2040 in vol. 3, PMID: 18446213.].

Escherichia coli strains adhere to the normally sterile human uroepithelium using type 1 pili, that are long, hairy surface organelles exposing a mannose-binding FimH adhesin at the tip. A small percentage of adhered bacteria can successfully invade bladder cells, presumably via pathways mediated by the high-mannosylated uroplakin-Ia and alpha3beta...

In vitro mimicking of the stimuli controlling in vivo-inducible bacterial promoters during infection of the host can be complex. Therefore, the use of the nematode Caenorhabditis elegans was evaluated, as a surrogate host to examine the expression of Salmonella enterica promoters. Green fluorescent protein (GFP+) was put under the control of the pr...

Bovine enterotoxigenic Escherichia coli (ETEC) carrying F17a fimbriae attach to the intestinal epithelium by means of the F17a-G adhesin. Since filamentous bacteriophages can be employed for the display of foreign peptides, we tested the applicability of this system to F17a-G. The receptor-binding domain of the F17a-G adhesin was expressed on bacte...

The insecticidal activity of the leaf (ASAL) and bulb (ASAII) agglutinins from Allium sativum L. (garlic) against the cotton leafworm, Spodoptera littoralis Boisd. (Lepidoptera: Noctuidae) was studied using transgenic tobacco plants expressing the lectins under the control of the constitutive CaMV35S promoter. PCR analysis confirmed that the garlic...

To check for correlation between the insecticidal properties and the specificity of lectins, a comparative study was made of the insecticidal activities of two garlic lectins with different biological activities. The insecticidal activity of the garlic (Allium sativum L.) leaf lectin ASAL and bulb lectin ASAII towards the tobacco aphid Myzus nicoti...

Three precisely defined deletion mutants of Salmonella enterica serovar Enteritidis were constructed, a guanine auxotrophic ΔguaB mutant, a nonflagellated ΔfliC mutant, and an auxotrophic and nonflagellated ΔguaB ΔfliC double mutant. All three mutants were less invasive than the wild-type strain in primary chicken cecal epithelial cells and the hum...

Salmonella Pathogenicity Island 1 (SPI-1) genes are indispensable for virulence of Salmonella Typhimurium in several animal species. The role of SPI-1 in the pathogenesis of Salmonella Typhimurium infections of pigs, however, is not well described. The interactions of a porcine Salmonella Typhimurium field strain and its isogenic mutants with disru...

Porcine carcasses contaminated with Salmonella typhimurium pose significant public health problems. Prolonged faecal shedding of Salmonella in pigs contributes to the contamination level of carcasses. Although the mechanism of prolonged faecal shedding is not yet clarified, the CS54 Island, and more specifically the shdA gene encoding a fibronectin...

SlyB is a small lipoprotein of 158 amino acids which is conserved in different Gram-negative bacteria. In contrast to other bacteria, where slyB is monocistronic, in Burkholderia multivorans and in B. cenocepacia, slyB is the last gene of an operon comprising three open reading frames encoding a putative thiol peroxidase, a putative sugar kinase an...

Salmonella Pathogenicity Island 1 (SPI-1) genes are indispensable for virulence of Salmonella Typhimurium in mice after oral challenge. These genes mediate invasion in intestinal epithelial cells and induce cell death in murine macrophages. The role of SPI-1 in the pathogenesis of Salmonella Typhimurium infections in food producing animals is not k...

The Red recombinase system of bacteriophage lambda has been used to inactivate chromosomal genes in E. coli K-12 through homologous recombination using linear PCR products. The aim of this study was to induce mutations in the genome of some temperate Shiga toxin encoding bacteriophages. When phage genes are in the prophage state, they behave like c...

Colibacillosis appears to be of increasing importance in layer flocks. The aim of this study was to determine characteristics of avian pathogenic Escherichia coli associated with the occurrence of colibacillosis outbreaks at flock level. Forty E. coli strains originating from layers from healthy flocks ('control isolates'), consisting of 25 caecal...

The development of the carrier state in swine after infection with Salmonella serovar Typhimurium (S. Typhimurium) has not been elucidated yet. Possibly, phagocytes like macrophages play a crucial role. It was the aim of the present study to characterize the interaction of a S. Typhimurium strain and its hilA and ssrA mutants with porcine periphera...