<p class="first" id="P1">EPEC is an attaching and effacing diarrheal pathogen that
carries a large pathogenicity
island, locus for enterocyte effacement (LEE). Recently, the pathogenicity island
PAI O-122 was described among non-LEE effectors and found to be associated with diarrhea
among atypical EPEC strains. It is unknown if incomplete PAI O-122 could be associated
with diarrhea duration and severity. To identify these virulence determinants we analyzed
379 EPEC strains isolated from Peruvian children. EPEC was diagnosed by PCR(eae+,
stx−) and classified as typical(t-EPEC) or atypical(a-EPEC). To characterize PAI O-122
we amplified three modules by PCR: Module 1(
<i>pagC</i>), Module 2(
<i>senA, nleB</i> and
<i>nleE</i>) and Module 3(
<i>lifA/efa-1</i>). To characterize the large ORF lifA/efa-1 we amplified the regions
known as efa-N,
efa-M and efa-C. Clinical information was obtained from the cohort study. A total
of 379 EPEC strains were able to analyze PAI O-122 genes, 128 (10.4%) EPEC strains
were isolated from 1235 diarrhea episodes and 251(9.2%) from 2734 healthy controls.
t-EPEC strains were isolated from 14.8% (19/128) of children with diarrhea and 25/251(10.0%)
from healthy controls. The most frequent PAI O-122 genes were
<i>nleE</i>(37.7%),
<i>senA</i>(34.6%) and
<i>nleB</i>(37.5%), with similar prevalence among diarrhea and control samples. However,
<i>lifA/efa-1</i> was more common among diarrhea cases than healthy control cases
(30.5% vs. 21.1%,
p<0.05). The presence of complete PAI O-122 was associated with diarrhea episodes
of higher severity among single pathogen infection (33.3% vs. 1.8%, p<0.05) mainly
due to the presence of a complete lifA/efa-1 gene. In summary, the gene lifA/efa-1
is significantly associated with diarrheal episodes of higher severity, suggesting
to be an important virulent factor.
</p>