Tissue tropism of enteropathogenic Escherichia coli strains belonging to the O55 serogroup.
Four enteropathogenic Escherichia coli (EPEC) strains belonging to the O55 serogroup (G21 and G30 [both O55:H6], G35 [O55:H-], and G58 [O55:H7]) were tested for their tissue tropism by using human intestinal in vitro organ culture. Strains showed restricted adhesion with attaching-and-effacing activity to follicle-associated epithelium of Peyer's patches, with no apparent adhesion to duodenum or colon. G35 and G58 express intimin gamma and show a similar tropism to intimin gamma-expressing enterohemorrhagic E. coli (EHEC) O157:H7. However, strains G21 and G30 were unusual because they expressed intimin alpha and had a restricted tissue tropism of intimin gamma phenotype. The amino acid sequence of the carboxy-terminal 280 amino acids of intimin from G21 was determined. Comparison with the prototype intimin alpha from strain E2348/69 (O127:H6) showed a single amino acid difference (corresponding to Val907 and Ala907 in the whole intimins). This mutation was reproduced by site-directed mutagenesis in an intimin alpha plasmid template, pCVD438, with the hypothesis that it may induce a change in tropism. However, when the mutated plasmid was placed in both EPEC and EHEC backgrounds, duodenal adhesion in a manner similar to strain E2348/69 was evident upon in vitro organ culture. Thus, additional factor(s) unrelated to intimin exist in the O55:H6 genome that influence human intestinal tissue tropism.
Centre for Paediatric Gastroenterology, Royal Free Hospital and University College Medical School, London, United Kingdom.
R J
RJ
Fitzhenry
S
S
Reece
L R
LR
Trabulsi
R
R
Heuschkel
S
S
Murch
M
M
Thomson
G
G
Frankel
A D
AD
Phillips
D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D007422:Intestines / Q000382:microbiology; D008969:Molecular Sequence Data; D009924:Organ Culture Techniques; D012703:Serotyping; D018523:Tropism / Q000502:physiology