title: The type VI secretion system plays a role in type 1 fimbria expression and pathogenesis of an avian pathogenic Escherichia coli strain.
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. Here we show that APEC strain SEPT362, isolated from a septicemic hen, expresses a type VI secretion system (T6SS); causes cytoskeleton rearrangements; and invades epithelial cells, replicates within macrophages, and causes lethal disease in chicks. To assess the contribution of the T6SS to SEPT362 pathogenesis, we generated two mutants, hcp (which encodes a protein suggested to be both secreted and a structural component of the T6SS) and clpV (encoding the T6SS ATPase). Both mutants showed decreased adherence and actin rearrangement on epithelial cells. However, only the hcp mutant presented a mild decrease in its ability to invade epithelial cells, and none of these mutants were defective for intramacrophage replication. 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 were attenuated for infection in chicks. These results suggest that the T6SS influences the expression of type 1 fimbriae and contributes to APEC pathogenesis.
authors.affiliation: Department of Genetics, Evolution, and Bioagents, Campinas State University (UNICAMP), Campinas, Sao Paulo, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: de Pace
authors.forename: Gerson
authors.initials: G
authors.lastname: Nakazato
authors.forename: Alline
authors.initials: A
authors.lastname: Pacheco
authors.forename: Jacqueline Boldrin
authors.initials: JB
authors.lastname: de Paiva
authors.forename: Vanessa
authors.initials: V
authors.lastname: Sperandio
authors.forename: Wanderley Dias
authors.initials: WD
authors.lastname: da Silveira
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D058947:Bacterial Secretion Systems / Q000502:physiology*; D002645:Chickens / Q000382:microbiology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006367:HeLa Cells / Q000382:microbiology; D006801:Humans; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D011201:Poultry Diseases / Q000382:microbiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018805:Sepsis / Q000382:microbiology / Q000662:veterinary
chemical_list: D058947:Bacterial Secretion Systems