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J Infect Dis. 2009 Jun 1;199(11):1689-97. doi: 10.1086/598524.

Role of the K2 capsule in Escherichia coli urinary tract infection and serum resistance.

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1
Department of Medicine, University of Maryland School of Medicine, MD, USA.

Abstract

BACKGROUND:

Capsule expression may be important during ascending Escherichia coli urinary tract infections (UTIs).

METHODS:

An isogenic ksl(k2)ABCDE mutant of extraintestinal pathogenic E. coli (ExPEC) strain CFT073 that could not synthesize the K2 capsule was compared with wild-type CFT073, to determine virulence in a murine model of ascending UTI and in vitro killing assays.

RESULTS:

No significant differences were observed regarding the abilities of the mutant and the wild-type CFT073 strains to colonize the murine urinary tract in single-challenge infection experiments. However, in competitive-colonization experiments, the mutant was significantly outcompeted by the wild-type strain in urine and the kidneys. The mutant strain was also more susceptible to human serum. Complementation of the mutant with a plasmid containing the ksl(k2)ABCDE genes restored capsule expression, enhanced survival in the murine urinary tract, and restored serum resistance.

CONCLUSION:

These results indicate that expression of the K2 capsule is important for the pathogenesis of UTI and provides protection against complement-mediated killing. To our knowledge, this is the first study in which the E. coli capsule has been proven to play a role in infection by use of isogenic mutants and genetic complementation.

PMID:
19432551
PMCID:
PMC3872369
DOI:
10.1086/598524
[Indexed for MEDLINE]
Free PMC Article
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