Invasiveness as a putative additional virulence mechanism of some atypical Enteropathogenic Escherichia coli strains with different uncommon intimin types.
BACKGROUND
Enteropathogenic Escherichia coli (EPEC) produce attaching/effacing (A/E) lesions on eukaryotic cells mediated by the outer membrane adhesin intimin. EPEC are sub-grouped into typical (tEPEC) and atypical (aEPEC). We have recently demonstrated that aEPEC strain 1551-2 (serotype O non-typable, non-motile) invades HeLa cells by a process dependent on the expression of intimin sub-type omicron. In this study, we evaluated whether aEPEC strains expressing other intimin sub-types are also invasive using the quantitative gentamicin protection assay. We also evaluated whether aEPEC invade differentiated intestinal T84 cells.


RESULTS
Five of six strains invaded HeLa and T84 cells in a range of 13.3%-20.9% and 5.8%-17.8%, respectively, of the total cell-associated bacteria. The strains studied were significantly more invasive than prototype tEPEC strain E2348/69 (1.4% and 0.5% in HeLa and T84 cells, respectively). Invasiveness was confirmed by transmission electron microscopy. We also showed that invasion of HeLa cells by aEPEC 1551-2 depended on actin filaments, but not on microtubules. In addition, disruption of tight junctions enhanced its invasion efficiency in T84 cells, suggesting preferential invasion via a non-differentiated surface.


CONCLUSIONS
Some aEPEC strains may invade intestinal cells in vitro with varying efficiencies and independently of the intimin sub-type.
Yamamoto
Denise
D
Universidade Federal de São Paulo, Rua Botucatu, 862, 3o andar, Vila Clementino, São Paulo, CEP 04023-062, Brazil. dyamamoto@unifesp.br
Hernandes
Rodrigo T
RT
Blanco
Miguel
M
Greune
Lilo
L
Schmidt
M Alexander
MA
Carneiro
Sylvia M
SM
Dahbi
Ghizlane
G
Blanco
Jesús E
JE
Mora
Azucena
A
Blanco
Jorge
J
Gomes
Tânia A T
TA
D008841:Actin Cytoskeleton / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000235:genetics*; D054308:Enteropathogenic Escherichia coli / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics*; D005798:Genes, Bacterial; D006367:HeLa Cells; D006801:Humans; D046529:Microscopy, Electron, Transmission; D012703:Serotyping; D019108:Tight Junctions / Q000378:metabolism; D014774:Virulence / Q000235:genetics*
D018829:Adhesins, Bacterial; D029968:Escherichia coli Proteins; C073819:eaeA protein, E coli