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


CONCLUSIONS
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.
Department of Medicine, University of Maryland School of Medicine, MD, USA.
Eric L
EL
Buckles
Xiaolin
X
Wang
M Chelsea
MC
Lane
C Virginia
CV
Lockatell
David E
DE
Johnson
David A
DA
Rasko
Harry L T
HL
Mobley
Michael S
MS
Donnenberg
D000818:Animals; D016667:Bacterial Capsules / Q000235:genetics*; D003001:Cloning, Molecular; D003360:Cosmids / Q000235:genetics; D017931:DNA Primers; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000097:blood / Q000235:genetics*; D006801:Humans; D051379:Mice; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D017384:Sequence Deletion; D014552:Urinary Tract Infections / Q000382:microbiology*
D017931:DNA Primers