Intimin type influences the site of human intestinal mucosal colonisation by enterohaemorrhagic Escherichia coli O157:H7.
BACKGROUND
Enterohaemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli epithelial cell adhesion is characterised by intimate attachment, and attaching and effacing (A/E) lesion formation. This event is mediated in part by intimin binding to another bacterial protein, Tir (translocated intimin receptor), which is exported by the bacteria and integrated into the host cell plasma membrane. Importantly, EPEC (O127:H6) and EHEC (O157:H7) express antigenically distinct intimin types known as intimin alpha and gamma, respectively. EHEC (O157:H7) colonises human intestinal explants although adhesion is restricted to the follicle associated epithelium of Peyer's patches. This phenotype is also observed with EPEC O127:H6 engineered to express EHEC intimin gamma.


OBJECTIVE
To investigate the influence of intimin on colonisation of human intestine by E coli O157:H7, and intimin types on tissue tropism in humans.


METHODS
Human intestinal in vitro organ culture with wild type and mutant strains of O157:H7 were employed.


RESULTS
Introducing a deletion mutation in the eae gene encoding intimin gamma in EHEC (O157:H7) caused the strain (ICC170) to fail to colonise human intestinal explants. However, colonisation of Peyer's patches and A/E lesion formation were restored with intimin gamma expression from a plasmid (ICC170 (pICC55)). In contrast, complementing the mutation with intimin alpha resulted in a strain (ICC170 (pCVD438)) capable of colonising and producing A/E lesions on both Peyer's patch and other small intestinal explants.


CONCLUSIONS
Intimin is necessary for human intestinal mucosal colonisation by E coli O157:H7. Intimin type influences the site of colonisation in a Tir type independent mechanism; intimin gamma appears to restrict colonisation to human follicle associated epithelium.
Fitzhenry
R J
RJ
Centre for Paediatric Gastroenterology, Department of Paediatrics and Child Health, Royal Free Hospital, London, UK.
Pickard
D J
DJ
Hartland
E L
EL
Reece
S
S
Dougan
G
G
Phillips
A D
AD
Frankel
G
G
D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003108:Colonic Diseases / Q000382:microbiology; D004378:Duodenal Diseases / Q000382:microbiology; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D005455:Fluorescent Antibody Technique; D017353:Gene Deletion; D006801:Humans; D007077:Ileal Diseases / Q000382:microbiology; D007413:Intestinal Mucosa / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D009154:Mutation / Q000235:genetics; D010581:Peyer's Patches / Q000648:ultrastructure; D010957:Plasmids
D018829:Adhesins, Bacterial; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C073819:eaeA protein, E coli