Hybrid and potentially pathogenic Escherichia coli strains - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 322

FIGURE 11.1 Adherence patterns of pathogenic Escherichia coli strains. Localized adherence
(LA), diffuse adherence (DA), and aggregative adherence (AA). Magnification: ×100.
backgrounds ( Escobar-Paramo et al., 2004 ), and have been associated with
enteric and urinary tract infections.
Epidemiology and global impact
There are several studies that investigated the involvement of DAEC in diar-
rheal disease and, overall, they indicated that this association is still unsettled.
Prevalence of DAEC isolates in stool samples of children with diarrhea is low
compared to other DEC pathotypes ( Gomez-Duarte et al., 2010 ; Rajendran
et al., 2010 ). Some studies have associated DAEC strains with diarrheal disease
in infants, children, and adults ( Giron et al., 1991 ; Jallat et al., 1993 ). Further,
an age-related incidence of DAEC strains expressing Afa/Dr adhesins has been
described, implicating DAEC as a cause of diarrhea, particularly in children
>12 months of age ( Gunzburg et al., 1993 ; Levine et al., 1993 ). On the other
hand, no differences in the frequency of DAEC strains were found in case-
control studies and no relation with the type or duration of diarrhea in children
was attributable to DAEC ( Gomes et al., 1989 ; Cravioto et al., 1991 ). More
strikingly, volunteer studies showed that DAEC strains orally administered
failed to induce diarrhea in adults ( Tacket et al., 1990 ).
A completely different situation is observed for DAEC strains associ-
ated with UTI infections. Afa/Dr DAEC strains are involved in 25-50% of
cystitis cases in children, 30% of pyelonephritis cases in pregnant women,
and one-third of recurrent UTIs in adults ( Archambaud et al., 1988 ; Daigle
et al., 1994 ). Moreover, a characterization of urinary E. coli isolates from 174
women with a first episode of UTI and assessment of the risk of a second UTI
indicated that Afa/Dr adhesins were associated with a two-fold increased risk
( Foxman et al., 1995 ). These observations have led to investigations about the
function of Afa/Dr adhesins in DAEC pathogenicity, to understand the mecha-
nism of DAEC interactions with the epithelia ( Servin, 2005 ; Le Bouguenec
and Servin, 2006 ).