Specific Adherence of Escherichia coli (Strain RDEC-1) to Membranous (M) Cells of the Peyer\u27s Patch in Escherichia coli Diarrhea in the Rabbit

The RDEC-1 strain Escherichia coli is an enteroadherent bacterium that produces diarrhea in the rabbit. A histopathologically similar disease has been described in humans. The RDEC-1 bacterium adheres to the epithelium of lymphoid follicles in rabbit ileal Peyer\u27s patches by 4 h postinoculation, 3-4 d before its adherence to absorptive epithelium. The purpose of this study was to determine whether the RDEC-1 bacterium adheres to a specific cell type in the lymphoid follicle epithelium. RDEC-1 bacteria were given in a dose of 2 X 10^6 by the orogastric route to postweanling rabbits. The distal ileal Peyer\u27s patch, taken from 5 control rabbits and 43 rabbits at intervals in the first 24 h postinoculation, was examined by routine and high-voltage electron microscopy. The RDEC-1 bacterium adhered specifically to M (membranous) rather than absorptive epithelial cells of the lymphoid follicle epithelium. Further understanding of how the bacterium attaches to M cells, which transport antigens to intraepithelial lymphocytes, could be useful in designing vaccines to protect mucosal surfaces

Peyer\u27s Patch Lymphoid Follicle Epithelial Adherence of a Rabbit Enteropathogenic Escherichia coli (Strain RDEC-1) Role of Plasmid-Mediated Pili in Initial Adherence

Escherichia coli (strain RDEC- 1) adheres to M cells of rabbit Peyer\u27s patch lymphoid follicle epithelium. The RDEC-1 strain contains an 85 X 10^6 D plasmid that codes for pili, which, when purified, adhere to gut absorptive epithelium. This study compared the in vivo lymphoid follicle adherence of the RDEC- 1 strain with that of a Shigella flexneri (ShD 15) that contained the 85 X 10^6 D plasmid and expressed the RDEC-l pili, a control E. coli, and a control S. flexneri (ShD 12). The bacteria were given in a dose of 10^10 to 0.7-1.1 kg rabbits. The rabbits were sacrificed at 2, 4, 6, and 12 h postinoculation. Peyer\u27s patch tissue was examined by electronmicroscopy and direct fluorescence microscopy. The piliated ShD 15 and RDEC-1 bacteria adhered in large numbers at 2 and 4 h postinoculation, but only the RDEC1 strain persisted and increased in numbers past that time. Control strains did not adhere. The ShD 15 strain adhered to and was rapidly taken into M cells, precipitating an acute inflammatory reaction within the follicle and adjacent lumen. Initial lymphoid follicle M cell adherence of the ShD 15 strain was associated with the possession of the adherence pilus plasmid. The failure of the ShD 15 strain to survive and colonize the lymph follicle epithelium contrasts with the success of the RDEC-1 strain and indicates that the RDEC-1 strain possesses virulence factors in addition to pili

Human intestinal tissue tropism of intimin epsilon O103 Escherichia coli

Human intestinal in vitro organ culture was used to assess the tissue tropism of human isolates of Escherichia coli O103:H2 and O103:H- that express intimin F. Both strains showed tropism for follicle associated epithelium and limited adhesion to other regions of the small and large intestine. This is similar to the tissue tropism shown by intimin gamma enterohaemorrhagic (EHEC) O157:H7, but distinct from that of intimin a enteropathogenic (EPEC) O127:H6. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserve

The EHEC Type III Effector NleL Is an E3 Ubiquitin Ligase That Modulates Pedestal Formation

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 causes hemorrhagic colitis and may result in potentially fatal hemolytic uremia syndrome in humans. EHEC colonize the intestinal mucosa and promote the formation of actin-rich pedestals via translocated type III effectors. Two EHEC type III secreted effectors, Tir and EspFu/TccP, are key players for pedestal formation. We discovered that an EHEC effector protein called Non-LEE-encoded Ligase (NleL) is an E3 ubiquitin ligase. In vitro, we showed that the NleL C753 residue is critical for its E3 ligase activity. Functionally, we demonstrated that NleL E3 ubiquitin ligase activity is involved in modulating Tir-mediated pedestal formation. Surprisingly, EHEC mutant strain deficient in the E3 ligase activity induced more pedestals than the wild-type strain. The canonical EPEC strain E2348/69 normally lacks the nleL gene, and the ectopic expression of the wild-type EHEC nleL, but not the catalytically-deficient nleL(C753A) mutant, in this strain resulted in fewer actin-rich pedestals. Furthermore, we showed that the C. rodentium NleL homolog is a E3 ubiquitin ligase and is required for efficient infection of murine colonic epithelial cells in vivo. In summary, our study demonstrated that EHEC utilizes NleL E3 ubiquitin ligase activity to modulate Tir-mediated pedestal formation.National Institutes of Health (U.S.) (grant AI078092)National Institutes of Health (U.S.) (grant AI068655