Enteropathogenic Escherichia coli - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 88

such as abdominal pain (80-90%), fever (20-60%), myalgia (20-30%), vomiting
(10-20%), and nausea (30-60%) ( Hedberg et al., 1997 ; Yatsuyanagi et al.,
2003 ) . In infants, dehydration is also common and severe cases may result in
weight loss, malnutrition, and death ( Levine, 1987 ; Donnenberg, 1995 ; Nataro
and Kaper, 1998 ; Fagundes-Neto and Andrade, 1999 ).
Complications
Children with EPEC are more likely to fail to respond to rehydration ther-
apy ( Fagundes-Neto and Scaletsky, 2000 ). Food intolerance is also prevalent
amongst infants <6 months ( Fagundes-Neto et al., 1996 ). These factors greatly
impact recovery from the chronic state and create a condition where mortality
rates may be as high 50% ( Rothbaum et al., 1983 ).
Diagnosis
Recent approaches towards diagnosing EPEC have been multifaceted; with
most current studies now undertaking both phenotypic and molecular analyses
to elucidate the pathotype of an infecting pathogen. In the past 15 years, there
has been an exponential increase in the number of publications working towards
the generation of an ideal set of genes with which to characterize EPEC strains.
However, the increase in the genomic libraries of these strains has further
increased our understanding of their genetic complexity. Hence, it appears that
a dual approach incorporating both phenotyping and genotyping will remain the
gold standard for some time. Furthermore, in many countries clinical laborato-
ries rarely perform tests required for EPEC identification, which remains the
purview of reference and research labs.
Traditionally EPEC strains were identified by their serotype. This method
has proven to be erroneous, as not all described EPEC serotypes display local-
ized adherence, or lack genes encoding Shiga toxins. Also, strains belonging to
non-EPEC serotypes, upon more extensive characterization, have been found
to display the current classifying features (see above). Presently, phenotypic
features used to identify EPEC strains are more focused on the defining actions
of the pathogen. The assessment of LA is a standard phenotypic diagnostic tool.
Complications arise however, when this method is utilized to diagnose a strain
that is atypical, as these strains do not exhibit typical LA ( Vieira et al., 2001 ;
Dulguer et al., 2003 ). Since EPEC induce the generation of actin-rich pedestals
in host cells, fluorescent-actin staining (FAS) as a means of pedestal detection
and a diagnostic technique has been included in a number of outbreak investiga-
tions and epidemiological studies of EPEC prevalence amongst food sources,
livestock, and domestic animals ( Knutton et al., 1991 ; Morelli et al., 1994 ;
Scotland et al., 1996 ; Saridakis et al., 1997 ; Rosa et al., 1998 ; Nakazato et al.,
2004 ; Carneiro et al., 2006 ). However, this method is limited by its inability to
differentiate EPEC from EHEC.