Gene or charac-teristic | Model 1 | Model 2 | Model 3 | ||||||
---|---|---|---|---|---|---|---|---|---|

β | P | OR | β | P | OR | β | P | OR | |

ehxA | − | − | − | − | − | − | − | − | − |

espP | −1.56 | 0.0094 | 0.21 | −1.43 | 0.035 | 0.14 | −1.60 | 0.0282 | 0.20 |

stx_{1} | −1.78 | 0.0006 | 0.17 | −1.94 | 0.0006 | 0.24 | −2.20 | 0.0046 | 0.11 |

stx_{2} | − | − | − | − | − | − | −1.88 | 0.0435 | 0.15 |

HEp-2 | 0.95 | 0.0047 | 2.59 | − | − | − | 1.22 | 0.0045 | 3.39 |

↵a Model 1, logistic regression model obtained by backward-elimination procedure and describing associations between STEC virulence factors and human isolates in comparison to bovine isolates; model 2, logistic regression model obtained by backward-elimination procedure and describing associations between virulence factors and isolates from severe disease in comparison to bovine isolates; model 3, logistic regression model obtained by backward-elimination procedure and describing the association between virulence factors and isolates from patients with uncomplicated diarrhea and healthy individuals in comparison to bovine isolates. The backward-elimination procedure had a threshold of 5% significance. HEp-2, level of adherence on HEp-2 cell cultures measured in proportion to a positive control; β, coefficient; −, variables not significant at the 5% level and not included in the model. The results indicate, for instance, that when all the other factors are kept constant, an

*espP*-positive isolate is five times less likely (equivalent to 0.20 times more likely) to originate from a healthy human or a human with simple diarrhea than from cattle (model 3). Similarly, for each increase of 100% in the adherence level (in comparison to the positive control), an isolate is 2.59 times more likely to originate from humans than from cattle (model 1).