Higher atypical enteropathogenic Escherichia coli (a-EPEC) bacterial loads in children with diarrhea are associated with PCR detection of the EHEC factor for adherence 1/lymphocyte inhibitory factor A (efa1/lifa) gene.
BACKGROUND
Typical enteropathogenic Escherichia coli (t-EPEC) are known to cause diarrhea in children but it is uncertain whether atypical EPEC (a-EPEC) do, since a-EPEC lack the bundle-forming pilus (bfp) gene that encodes a key adherence factor in t-EPEC. In culture-based studies of a-EPEC, the presence of another adherence factor, called EHEC factor for adherence/lymphocyte activation inhibitor (efa1/lifA), was strongly associated with diarrhea. Since a-EPEC culture is not feasible in clinical laboratories, we designed an efa1/lifA quantitative PCR assay and examined whether the presence of efa1/lifA was associated with higher a-EPEC bacterial loads in pediatric diarrheal stool samples.


METHODS
Fecal samples from children with diarrhea were tested by qPCR for EPEC (presence of eae gene) and for shiga toxin genes to exclude enterohemorrhagic E. coli, which also contain the eae gene. EPEC containing samples were then tested for the bundle-forming pilus gene found in t-EPEC and efa1/lifA. The eae gene quantity in efa1/lifA-positive and negative samples was compared.


RESULTS
Thirty-nine of 320 (12%) fecal samples tested positive for EPEC and 38/39 (97%) contained a-EPEC. The efa1/lifA gene was detected in 16/38 (42%) a-EPEC samples. The median eae concentration for efa1/lifA positive samples was significantly higher than for efa1/lifA negative samples (median 16,745 vs. 1183 copies/µL, respectively, p = 0.006).


CONCLUSIONS
Atypical enteropathogenic E. coli-positive diarrheal stool samples containing the efa1/lifA gene had significantly higher bacterial loads than samples lacking this gene. This supports the idea that efa1/lifA contributes to diarrheal pathogenesis and suggests that, in EPEC-positive samples, efa/lifA may be a useful additional molecular biomarker.
Department of Laboratory Medicine and Pathology, Children's Hospital of Eastern Ontario, University of Ottawa, 401 Smyth Rd, Ottawa, ON, K1H 8L1, Canada. slinger@cheo.on.ca.
Robert
R
Slinger
McMaster University, Hamilton, ON, Canada.
Kimberley
K
Lau
Department of Laboratory Medicine and Pathology, Children's Hospital of Eastern Ontario, University of Ottawa, 401 Smyth Rd, Ottawa, ON, K1H 8L1, Canada.
Michael
M
Slinger
Department of Laboratory Medicine and Pathology, Children's Hospital of Eastern Ontario, University of Ottawa, 401 Smyth Rd, Ottawa, ON, K1H 8L1, Canada.
Ioana
I
Moldovan
Department of Laboratory Medicine and Pathology, Children's Hospital of Eastern Ontario, University of Ottawa, 401 Smyth Rd, Ottawa, ON, K1H 8L1, Canada.
Francis
F
Chan
D000293:Adolescent; D058491:Bacterial Load; D001427:Bacterial Toxins / Q000032:analysis* / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D003967:Diarrhea / Q000175:diagnosis / Q000382:microbiology*; D054308:Enteropathogenic Escherichia coli / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000175:diagnosis / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000032:analysis* / Q000235:genetics; D005243:Feces / Q000382:microbiology; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011446:Prospective Studies; D060888:Real-Time Polymerase Chain Reaction
D001427:Bacterial Toxins; C404907:Efa1 protein, E coli; D029968:Escherichia coli Proteins; C406587:lymphostatin protein, E coli
Diarrhea; Enteropathogenic Escherichia coli; Gastroenteritis; Real-time PCR