Uropathogenic Escherichia coli - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 273

Ygi fimbriae,
Ygi fimbriae are encoded by 61% of UPEC isolates as compared to 24% fecal
E. coli strains, suggesting these fimbriae may be urovirulence factors ( Spurbeck
et al., 2011 ). Deletion of the ygi operon from the pyelonephritis strain E. coli
CFT073 was sufficient to reduce adherence to the human kidney epithelial cell
line, HEK 293, and reduce biofilm formation on abiotic surfaces ( Spurbeck
et al., 2011 ). These deficiencies were fully complemented by introduction of
the ygi operon on a plasmid. Ygi fimbriae are expressed both in LB medium
and in human urine. In the mouse model of ascending UTI, the ygi deletion
mutant was outcompeted by wild-type E. coli CFT073 in the kidneys of mice
and this phenotype was fully complementable, fulfilling molecular Koch's pos-
tulates, demonstrating that these fimbriae are involved in the pathogenesis of
UTI ( Spurbeck et al., 2011 ).
Yad fimbriae
Yad fimbriae are encoded by 46% of UPEC compared to 21% fecal E. coli
strains ( Spurbeck et al., 2011 ). Deletion of the yad operon from E. coli
CFT073 resulted in diminished adherence to the human bladder epithelial
cell line, UM-UC-3, biofilm formation on abiotic surfaces, and motility
( Spurbeck et al., 2011 ). Furthermore, Yad fimbriae are expressed when the
bacteria are cultured in human urine, and a double mutant, in which both
the yad and ygi fimbrial operons are deleted from the chromosome, was out-
competed by wild-type E. coli CFT073 in bladder and kidneys of the mouse
model of ascending UTI. Since the ygi deletion mutant alone is only out-
competed by wild-type E. coli CFT073 in the kidneys, this suggests that Yad
fimbriae, along with Ygi fimbriae, are involved in colonization of the bladder
( Spurbeck et al., 2011 ).
Auf fimbriae
Auf fimbriae ( a nother u pec f fimbriae, encoded by aufABCDEFG ) are encoded
by 67% of UPEC compared to 27% fecal E. coli strains ( Spurbeck et al., 2011 ).
Auf fimbriae, when expressed in E. coli BL21-AI cells, did not agglutinate
human, guinea pig, or sheep erythrocytes, nor mediate adherence to T24 blad-
der epithelial cells or HEp-2 laryngeal carcinoma cells ( Buckles et al., 2004 ).
Although the auf operon is transcribed by E. coli CFT073 and 10 other UPEC
strains, no protein was detected by immunoblot in vitro. After mice were infected
with either wild-type E. coli CFT073 or an aufC mutant, the mice infected with
the wild-type strain elicited an immune response to AufA antigen as detected
by ELISA, whereas only 1 out of 10 mice infected with the mutant strain had
an immune response. This suggested that Auf fimbriae are synthesized in vivo
( Buckles et al., 2004 ). However, results from the mouse model of ascending
UTI demonstrate that Auf fimbriae do not play a significant role in colonization,
as there was no significant difference in colonization between wild-type E. coli