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BioMed Research International
Volume 2014 (2014), Article ID 797508, 9 pages
Research Article

Analysis of the Virulence of an Atypical Enteropathogenic Escherichia coli Strain In Vitro and In Vivo and the Influence of Type Three Secretion System

1Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Escola Paulista de Medicina, Rua Botucatu 862, 3rd floor, Vila Clementino, 04023-062 São Paulo, SP, Brazil
2Departamento de Cirurgia, Universidade Federal de São Paulo, Escola Paulista de Medicina, Rua Pedro de Toledo 781, 9th floor, Vila Clementino, 04039-032 São Paulo, SP, Brazil
3Departamento de Ornitopatologia, Faculdade de Medicina Veterinária, Universidade de São Paulo, Avenida Prof. Dr. Orlando Marques de Paiva 87, Cidade Universitária, 05508-900 São Paulo, SP, Brazil
4Departamento de Microbiologia e Imunologia, Instituto de Biociências, UNESP, Distrito de Rubião Junior s/n, Botucatu, 18618-970 São Paulo, SP, Brazil
5Fleury Medicina e Saúde, Avenida General Valdomiro de Lima 508, 04344-903 São Paulo, SP, Brazil
6Centro de Microscopia Eletrônica, Universidade Federal de São Paulo, Escola Paulista de Medicina, Rua Botucatu 862, 1 st floor, 04023-062 São Paulo, SP, Brazil

Received 7 February 2014; Accepted 5 April 2014; Published 28 April 2014

Academic Editor: Chensong Wan

Copyright © 2014 Suely C. F. Sampaio et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Atypical enteropathogenic Escherichia coli (aEPEC) inject various effectors into intestinal cells through a type three secretion system (T3SS), causing attaching and effacing (A/E) lesions. We investigated the role of T3SS in the ability of the aEPEC 1711-4 strain to interact with enterocytes in vitro (Caco-2 cells) and in vivo (rabbit ileal loops) and to translocate the rat intestinal mucosa in vivo. A T3SS isogenic mutant strain was constructed, which showed marked reduction in the ability to associate and invade but not to persist inside Caco-2 cells. After rabbit infection, only aEPEC 1711-4 was detected inside enterocytes at 8 and 24 hours pointing to a T3SS-dependent invasive potential in vivo. In contrast to aEPEC 1711-4, the T3SS-deficient strain no longer produced A/E lesions or induced macrophage infiltration. We also demonstrated that the ability of aEPEC 1711-4 to translocate through mesenteric lymph nodes to spleen and liver in a rat model depends on a functional T3SS, since a decreased number of T3SS mutant bacteria were recovered from extraintestinal sites. These findings indicate that the full virulence potential of aEPEC 1711-4 depends on a functional T3SS, which contributes to efficient adhesion/invasion in vitro and in vivo and to bacterial translocation to extraintestinal sites.