Initial adherence of EPEC, EHEC and VTEC to host cells

Initial adherence to host cells is the first step of the infection of enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic Escherichia coli (EHEC) and verotoxigenic Escherichia coli (VTEC) strains. The importance of this step in the infection resides in the fact that (1) adherence is the first contact between bacteria and intestinal cells without which the other steps cannot occur and (2) adherence is the basis of host specificity for a lot of pathogens. This review describes the initial adhesins of the EPEC, EHEC and VTEC strains. During the last few years, several new adhesins and putative colonisation factors have been described, especially in EHEC strains. Only a few adhesins (BfpA, AF/R1, AF/R2, Ral, F18 adhesins) appear to be host and pathotype specific. The others are found in more than one species and/or pathotype (EPEC, EHEC, VTEC). Initial adherence of EPEC, EHEC and VTEC strains to host cells is probably mediated by multiple mechanisms

Lipopolysaccharide of Escherichia coli : structure, biosynthesis and functions

The lipopolysaccharide (LPS) is a major component of the surface of the Gram negative bacteria. The LPS is composed of three separately synthesized entities: the lipid A, the core oligosaccharide and the O antigen, that will be linked together after their respective synthesis. The lipid A, embedded inside the outer membrane, is the proximal part of the LPS and the core is the medial part, whereas the O antigen represents the distal part free in the external environment. Amongst the Enterobacteriaceae family, the lipid A is structurally highly conserved and the variation in the structure of the core oligosaccharide is limited whereas the O antigen is the hypervariable region. Diverse biological activities have been associated with LPS, amongst which the endotoxinic activity carried by the lipid A, and the strain immunogenic specificity carried by the O antigen. In this review manuscript we summarize the state of knowledge on the structures and biosynthesis of the different components of the LPS of Escherichia coli and on their respective roles in the virulence of pathogenic bacteria

Pneumonia with Aeromonas sobria in a Carpet Python

Aeromonas sobria was isolated and identified upon post-mortem examination from the respiratory tract and the blood of a carpet python (Morelia spilota variegata). The snake was referred to the Faculty of Veterinary Medicine of Liège for necropsy, just the day after it suddenly died without previous clinical sign. Lung and liver biopsies were performed and fixed in neutral buffered 10% formalin and paraffin embedded. Blood samples were collected via cardiocentesis, and air sac abscesses were cultured. Bacterial strains were identified as Aeromonas sobria by 16S rDNA sequencing. Based on histological and bacterial examinations, the death of this snake was attributed to a septicemia, following an acute primary, or secondary exudative pneumonia. Aeromonas sp. is established as a potential pathogen in reptiles. Among this genus, Aeromonas hydrophila is the most frequently isolated. A. sobria has been reported as a primary pathogen in farmed perch (Perca fluviatilis) and humans. Conversely, few data are available concerning the pathogenicity of A. sobria in reptiles. Other non-bacterial agents (virus, fungus, endoparasites) or predisposing factors (such as obesity) can also be responsible for respiratory tract disease in snakes . Unfortunately, in the current case, virological investigations were not performed

Bacterial sspecies found in TEC3 following restriction fragment length polymorphism analysis of polymerase chain reaction-amplified 16S ribosomal RNA genes

peer reviewe

Presence in bovine enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherichia coli of genes encoding for putative adhesins of human EHEC strains

Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC) infections are characterised by the formation of attaching and effacing lesions on intestinal epithelial cells. The first step of EPEC and EHEC pathogenesis involves the initial adherence of the bacterium to the intestinal epithelium. A collection of bovine EPEC and EHEC strains belonging to different serogroups was tested by colony blot hybridization with gene probes for putative adhesins (BFPA, LPFA, IHA, LIFA) of human EPEC and EHEC, and also for fimbrial and afimbrial adhesins (AFA8, F17, Cs31A) of bovine necrotoxigenic E. coli (NTEC). In the bovine EPEC and EHEC strains tested, sequences homologous to lifA, ihA, and lpfA genes were detected, sometimes in association with particular serogroups. Bovine O26 EPEC also possessed a sequence homologous to a gene of the clp operon, coding for the CS31A adhesin, associated with bovine NTEC. Overall results showed that different genes encoding for putative adhesins of human EHEC strains are present in bovine EPEC and EHEC strains, but not one of them is present in all strains

L'entéropathie épizootique du lapin est elle une pathologie bactérienne?

peer reviewedThe etiology of epizootic rabbit enteropathy (ERE) is still unknown despite ten years of continuous research. A putative bacterial etiology is at the basis of current research. The fractionation of the reference inoculum (TEC4) is a major step to find the potential bacterial agent(s). In this study, TEC4 was fractionated with two techniques: centrifugation on discontinuous sucrose gradient then cell adhesion. Two selected fractions were inoculated to SPF rabbits and analyzed with classical bacteriological techniques. ERE was reproduced with both fractions. The 16S rDNA gene was amplified in all fractions and in three negative controls and subsequently analyzed with Restriction Fragment Length Polymorphism (RFLP) and Denaturating Gradient Gel Electrophoresis (DGGE). A difference in bacterial DNA composition was found between virulent and non-virulent fractions which reinforce the potential role of bacteria in the etiology of ERE.Identification moléculaire des bactéries impliquées dans l’entéropathie épizootique du lapin européen (Oryctolagus cuniculus) et développement d’une prophylaxie vaccinal