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Infect Immun. 2015 May;83(5):1749-64. doi: 10.1128/IAI.02810-14. Epub 2015 Feb 9.

Molecular analysis of asymptomatic bacteriuria Escherichia coli strain VR50 reveals adaptation to the urinary tract by gene acquisition.

Author information

1
Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia s.beatson@uq.edu.au m.schembri@uq.edu.au.
2
Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia.
3
Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
4
Centre for Biological Sequence Analysis, DTU Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark.
5
School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia Griffith Health Institute and School of Medical Science, Griffith Health Centre, Griffith University, Gold Coast, Queensland, Australia.

Abstract

Urinary tract infections (UTIs) are among the most common infectious diseases of humans, with Escherichia coli responsible for >80% of all cases. One extreme of UTI is asymptomatic bacteriuria (ABU), which occurs as an asymptomatic carrier state that resembles commensalism. To understand the evolution and molecular mechanisms that underpin ABU, the genome of the ABU E. coli strain VR50 was sequenced. Analysis of the complete genome indicated that it most resembles E. coli K-12, with the addition of a 94-kb genomic island (GI-VR50-pheV), eight prophages, and multiple plasmids. GI-VR50-pheV has a mosaic structure and contains genes encoding a number of UTI-associated virulence factors, namely, Afa (afimbrial adhesin), two autotransporter proteins (Ag43 and Sat), and aerobactin. We demonstrated that the presence of this island in VR50 confers its ability to colonize the murine bladder, as a VR50 mutant with GI-VR50-pheV deleted was attenuated in a mouse model of UTI in vivo. We established that Afa is the island-encoded factor responsible for this phenotype using two independent deletion (Afa operon and AfaE adhesin) mutants. E. coli VR50afa and VR50afaE displayed significantly decreased ability to adhere to human bladder epithelial cells. In the mouse model of UTI, VR50afa and VR50afaE displayed reduced bladder colonization compared to wild-type VR50, similar to the colonization level of the GI-VR50-pheV mutant. Our study suggests that E. coli VR50 is a commensal-like strain that has acquired fitness factors that facilitate colonization of the human bladder.

PMID:
25667270
PMCID:
PMC4399054
DOI:
10.1128/IAI.02810-14
[Indexed for MEDLINE]
Free PMC Article

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