Signature-tagged mutagenesis in a chicken infection model leads to the identification of a novel avian pathogenic Escherichia coli fimbrial adhesin

The extraintestinal pathogen, avian pathogenic E. coli (APEC), known to cause systemic infections in chickens, is responsible for large economic losses in the poultry industry worldwide. In order to identify genes involved in the early essential stages of pathogenesis, namely adhesion and colonizati...

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Bibliographic Details
Published in:	PloS one 2009-11, Vol.4 (11), p.e7796-e7796
Main Authors:	Antão, Esther-Maria, Ewers, Christa, Gürlebeck, Doreen, Preisinger, Rudolf, Homeier, Timo, Li, Ganwu, Wieler, Lothar H
Format:	Article
Language:	eng
Subjects:	Adhesins Adhesins, Escherichia coli - metabolism Animals Appendages Bacteria Birds Chickens Clonal deletion Cloning Colonization Complementation Dogs E coli Economic impact Electron microscopy Epithelial cells Escherichia coli Escherichia coli - genetics Escherichia coli - metabolism Escherichia coli Infections - metabolism Evolutionary Biology Fibroblasts Fibroblasts - metabolism Fimbriae, Bacterial - metabolism Gene Deletion Genes Genetic Complementation Test Genetics and Genomics Genomes Health aspects Health care Identification Immunization Infection Infections Infectious Diseases Intestine Lungs Microbiology Microscopy, Electron - methods Molecular Biology Multigene Family Multilocus sequence typing Mutagenesis Mutants Mutation Pathogenesis Pathogens Phylogenetics Positive selection Poultry Poultry industry Pseudomonas syringae Short term memory Signature-tagged mutagenesis Veterinary medicine Y chromosomes
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Summary:	The extraintestinal pathogen, avian pathogenic E. coli (APEC), known to cause systemic infections in chickens, is responsible for large economic losses in the poultry industry worldwide. In order to identify genes involved in the early essential stages of pathogenesis, namely adhesion and colonization, Signature-tagged mutagenesis (STM) was applied to a previously established lung colonization model of infection by generating and screening a total of 1,800 mutants of an APEC strain IMT5155 (O2:K1:H5; Sequence type complex 95). The study led to the identification of new genes of interest, including two adhesins, one of which coded for a novel APEC fimbrial adhesin (Yqi) not described for its role in APEC pathogenesis to date. Its gene product has been temporarily designated ExPEC Adhesin I (EA/I) until the adhesin-specific receptor is identified. Deletion of the ExPEC adhesin I gene resulted in reduced colonization ability by APEC strain IMT5155 both in vitro and in vivo. Furthermore, complementation of the adhesin gene restored its ability to colonize epithelial cells in vitro. The ExPEC adhesin I protein was successfully expressed in vitro. Electron microscopy of an afimbriate strain E. coli AAEC189 over-expressed with the putative EA/I gene cluster revealed short fimbrial-like appendages protruding out of the bacterial outer membrane. We observed that this adhesin coding gene yqi is prevalent among extraintestinal pathogenic E. coli (ExPEC) isolates, including APEC (54.4%), uropathogenic E. coli (UPEC) (65.9%) and newborn meningitic E. coli (NMEC) (60.0%), and absent in all of the 153 intestinal pathogenic E. coli strains tested, thereby validating the designation of the adhesin as ExPEC Adhesin I. In addition, prevalence of EA/I was most frequently associated with the B2 group of the EcoR classification and ST95 complex of the multi locus sequence typing (MLST) scheme, with evidence of a positive selection within this highly pathogenic complex. This is the first report of the newly identified and functionally characterized ExPEC adhesin I and its significant role during APEC infection in chickens.
ISSN:	1932-6203 1932-6203