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| Author(s): |
Fernanda de Pace
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2011-03-03 |
| Examining board members: |
Wanderley Dias da Silveira;
Luciana Maria de Hollanda;
Marcelo de Carvalho Ramos;
Fabiana Horn;
Vasco Ariston de Carvalho Azevedo
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| Advisor: | Wanderley Dias da Silveira; Eliana Guedes Stehling |
| Abstract | |
Avian pathogenic Escherichia coli (APEC) strains frequently cause extraintestinal infections and are responsible for significant economic losses in the poultry industry worldwide. APEC isolates are closely related to human extraintestinal pathogenic E. coli (ExPEC) strains and may also act as pathogens for humans. Known APEC virulence factors include adhesins such as type 1 fimbriae and curli, iron acquisition systems, and cytotoxins, among others. Here we demonstrated that APEC strain SEPT362, isolated from a septicemic hen, expresses a type VI secretion system (T6SS), causes cytoskeleton rearrangements, invades epithelial cells, replicates within macrophages, and causes lethal disease in chicks. To assess the contribution of the T6SS to SEPT362 pathogenesis, we generated three mutants, ?hcp (which encodes a protein suggessed to be both secreted and a structural component of the T6SS), ?clpV (encoding the T6SS ATPase) and ?icmF (intracellular multiplication factor). All mutants showed decreased adherence and invasion to HeLa cells and decrease in several other pathogenicity related characteristics. Transcriptome studies showed that the level of expression of type 1 fimbriae was decreased in these mutants, which may account for the diminished adhesion and invasion of epithelial cells. The T6SS seems to be important for the disease process, given that both mutants (?hcp and ?clpV) were attenuated in an infection model in chicks. These results suggest that the T6SS influences the expression of type 1 fimbriae and contributes to the pathogenesis of this APEC strain pathogenesis (AU) | |