Biology Reference
In-Depth Information
Chapter 4
Enteropathogenic
Escherichia coli
Shahista Nisa, Karen M. Scanlon, and Michael S. Donnenberg
University of Maryland School of Medicine, Baltimore, MD, USA
BACKGROUND
Definition and classification
Enteropathogenic
E. coli
(EPEC) strains are diarrhea-causing, non-Shiga-toxin-
producing
E. coli
. In healthy adults, EPEC-induced diarrhea may be initiated by
a dose of 10
8
to 10
10
CFU, though this infectious dose is likely lower for chil-
dren (
Donnenberg et al., 1998
). Upon intimate attachment, these strains efface
the host cell microvilli, generating a characteristic histopathology known as the
attaching and effacing (A/E) effect. In these ways, EPEC is distinguished from
other diarrheagenic pathotypes, as enteroaggregative
E. coli
(EAEC), enteroin-
vasive
E. coli
(EIEC), and enterotoxigenic
E. coli
(ETEC) do not display an A/E
effect, while enterohemorrhagic
E. coli
(EHEC) express Shiga toxins (
Nataro
and Kaper, 1998
). The genetic elements responsible for the production of A/E
pathology are harbored on a large pathogenicity island known as the
l
locus of
e
nterocyte
e
ffacement (LEE) (
McDaniel and Kaper, 1997
). In addition, EPEC
strains are further classified as typical or atypical by the presence or absence of
an
E
PEC
a
dherence
f
factor (EAF) plasmid encoding the BFP.
History
In the 1930s, serological methods were used to characterize
E. coli
infections
among both infants and calves, but the significance of
E. coli
in diarrheal dis-
ease was not fully appreciated until 1945 (
Taylor, 1961
). Bray associated spe-
cific
E. coli
, later recognized as serogroup O111, with an outbreak of infantile
diarrhea, and this was quickly succeeded by a number of publications which
further established the importance of O111 and extended the implicated sero-
groups to include O55, O26, and O119 (
Bray, 1945
). In the 1950s, with the
advent of an internationally accepted serological testing method, it was soon
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