Journal of Clinical Microbiology, Sep 1996, 2053-2057, Vol 34, No. 9
D Reymond, RP Johnson, MA Karmali, M Petric, M Winkler, S Johnson, K Rahn, S Renwick, J Wilson, RC Clarke and J Spika
An enzyme-linked immunosorbent assay (ELISA) to detect antibodies to
Escherichia coli O157 lipopolysaccharide (LPS) was developed with sera from
63 children with confirmed recent E. coli O157 infection and from 256
age-stratified urban controls. The median ELISA values for control and case
sera were 0.05 (interquartile range, 0 to 0.20; mean +/- standard deviation
[SD], 0.15 +/- 0.22) and 1.41 (interquartile range, 1.11 to 1.59; mean +/-
SD, 1.41 +/- 0.53), respectively (P < 0.001). With a breakpoint of 0.59
(mean ELISA value of the control sera + 2 SDs), the assay had a
sensitivity, specificity, and positive and negative predictive values of
95, 94, 80, and 98%, respectively, for recent E. coli O157 infection. The
O157 LPS assay and Vero cytotoxin (VT) 1-neutralizing-antibody (NAb) assay
were used to compare the relative frequencies of O157 LPS antibodies and
VT1-NAbs in an age- stratified urban population from Toronto, Ontario,
Canada, and in 216 healthy family members from dairy farm in southern
Ontario. The frequency of O157 LPS antibodies was about threefold higher in
dairy farm residents (12.5%) than in urban residents (4.7%) (P < 0.01).
Similarly, the frequency of VT1-NAbs was about sixfold higher in dairy farm
residents (42.0%) than in urban residents (7.7%) (P < 0.001). These
findings are consistent with a greater level of exposure of dairy farm
residents to VT-producing E. coli (VTEC) strains. The high rate of
seropositivity to VT1 in farm residents probably reflects the booster
effect of repeated VTEC exposures and argues against a sustained
generalized immunosuppressive effect of VT1. Seroepidemiological studies
may help in assessing the level of exposure of different populations to
VTEC strains.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Neutralizing antibodies to Escherichia coli Vero cytotoxin 1 and antibodies to O157 lipopolysaccharide in healthy farm family members and urban residents
Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
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