Meningitis-associated Escherichia coli - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 300

Fimbriae
Our experiment with an E. coli DNA microarray comparing the gene expression
patterns of HBMEC-associated versus non-associated E.coli K1 revealed that
type 1 fimbriae play an important role in E. coli K1 binding to HBMEC ( Teng
et al., 2005 ). The HBMEC-associated E. coli K1 showed significantly higher
expression levels of the fim cluster genes compared to non-associated bacteria.
Expression of type 1 fimbriae in wild-type E. coli is regulated by phase variation
in which each bacterium can alternate between fimbriated and non-fimbriated
states, so-called phase-ON and phase-OFF, respectively (see Chapter 12). We
have shown that E. coli K1 associated with HBMEC are predominantly type
1 fimbriae phase-ON bacteria. We constructed type 1 fimbria locked-ON and
locked-OFF mutants of E. coli K1 strain RS218, whose fim promoters are fixed
in the ON and OFF orientations, respectively, and showed that E. coli K1 bind-
ing to HBMEC is significantly greater with the locked-ON mutant than the
wild-type strain, while it is significantly less with the locked-OFF mutant ( Teng
et al., 2005 ). Decreased binding as the result of the fimH deletion or the locked-

TABLE 10.2 Development of bacteremia and meningitis (defined as
positive CSF cultures) in newborn rats receiving meningitis-causing E. coli
K1 strain RS218 or its deletion mutants

E. coli
strain

No. of
animals

Bacteremia (log
CFU/ml blood)

No (% of animals
with positive CSF) References

RS218 19 7.18 + 0.63 12 (63) Wang and Kim, 2002

Δ ompA 22 7.05 + 0.49 6 (27) a

RS218 24 7.51 + 1.25 16 (67) Huang et al., 1995

4 (16) a

Δ ibeA 25 6.97 + 1.21

RS218 27 7.01 + 1.17 15 (56) Huang et al., 1999

Δ ibeB 25 7.06 + 1.29 4 (16) a

RS218 24 7.53 + 0.40 18 (75) Wang et al., 1999

Δ ibeC 24 7.80 + 0.67 10 (42) a

RS218 17 7.50 + 0.32 14 (82) Hoffman et al., 2000

22 7.60 + 0.49 7 (32) a

Δ aslA

RS218 26 7.64 + 1.00 20 (77) Khan et al., 2002

Δ cnf1 27 7.24 + 1.60 12 (44) a

a Signiicantly less than RS218.
Modified with permission from Infection and Immunity ( Kim, 2001 ).