Biology Reference
In-Depth Information
strain, and that multiple genes and genomic regions contribute to the fitness of
CFT073 in the urinary tract.
Later in 2009, two more UPEC strains, UMN026 and IAI39, were sequenced
by
Touchon et al. (2009)
. UMN026 was isolated from the urine of a patient
with cystitis. The genome contains 5.2 Mbps with 4918 protein-coding genes,
and two plasmids; one plasmid was 122 kb with 149 protein-coding genes and
the other was 34 kb with 54 protein-coding genes. IAI39 was isolated from the
urine of a patient with pyelonephritis. The genome consists of 5.1 Mbps, 4906
protein-coding genes, and no plasmids. This group compared UMN026, IAI39,
and the three previously published UPEC genomes with 15 other diarrheagenic
or commensal
E. coli
strains (
Touchon et al., 2009
). When considering intrin-
sic extraintestinal virulence (in a mouse model of bacteremia) (
Johnson et al.,
2006
), the authors were not able to identify any single genes that were specific to
a virulent phenotype (
Touchon et al., 2009
). This demonstrated that the distinct
pathogenic potential of UPEC, as compared to other
E. coli
, was not the result
of a fixed group of virulence factors, but rather a variable collection of factors.
More recently, in 2010, Hagan et al. published the first transcriptional pro-
file of pathogenic
E. coli
taken directly from patients with a naturally occurring
infection (
Hagan et al., 2010
). Isolates were collected from the urine of eight
women with bacteriuria, and the transcriptomes were compared by microarray
to the same isolates grown statically in sterilized urine. When these data were
compared to gene expression data from a mouse model (
Snyder et al., 2004
),
there was an overall positive correlation. Iron acquisition genes and metabolic
genes were most strongly correlated with colonization, toxin genes were moder-
ately correlated, but fimbriae and adhesion genes were poorly correlated. Mul-
tiple fimbriae genes are highly expressed by CFT073 in mice, including the
fim
operon. Despite being highly expressed in mice, only two of six isolates tested
from humans expressed the
fim
operon in the urine, even though seven of the
eight strains were confirmed to make functional fimbria. These findings dem-
onstrate that while the mouse model largely reflects the transcriptional profile
of UPEC in humans, there are some differences, and continued study of UPEC
transcriptomics may lead to more effective therapeutics (
Hagan et al., 2010
).
New approaches to studying global changes in gene expression, such as RNA-
seq, will further our understanding of UPEC pathogenesis. While genomic analyses
have demonstrated that there is variable collection of virulence factors that confer
pathogenic potential to UPEC isolates, the coordinated expression of these factors
is also likely to influence pathogenesis. Further study of UPEC transcriptomics may
identify novel virulence factors and targets for vaccine and therapeutic development.
SHIGA-TOXIN PRODUCING
E. COLI/
ENTEROHEMORRHAGIC
E. COLI
(STEC/EHEC)
The Shiga toxin, encoded by a lambdoid prophage in
E. coli
isolates (
Campbell
et al., 1992
), was first characterized in an epidemic case of dysentery caused by
Search WWH ::
Custom Search