One or more putative enteroaggregative Escherichia coli (EAEC)
virulence factors (
aggA, aggR,
aspU, or aafA) were identified in 60 (70%) of 86 EAEC isolates from travelers with
diarrhea compared with a rate of 7 (8%) of 90 in patients with
diarrhea who were infected with nonadherent E. coli (odds ratio, 27.36; 95% confidence interval, 11.30 to 65.91). The presence of aggR or one or more
virulence factors in EAEC from patients with
diarrhea was associated with a statistically increased concentration of
interleukin-8 (IL-8) in feces compared with that in EAEC negative for these factors: for aggR positive (9 of 12 [75%]; median, 800 pg/ml) versus aggR negative (5 of 18 [28%]; median, 0), P < 0.05; and for isolates positive for > or =1
virulence factor (13 of 21 [62%]; median, 360 pg/ml) versus those negative for > or =1
virulence factor (1 of 9 [11%]; median, 0), P < 0.05. Other fecal
cytokines (IL-1beta and IL-1ra) were found in increased concentrations (P < 0.05 when at least one EAEC
virulence factor was present compared with the concentrations when EAEC negative for multiple
virulence factors was found in patients with
diarrhea. Putative
virulence factors were commonly found in EAEC from patients with
diarrhea, and the pathogenicity of many strains was suggested by showing an association between the presence of plasmid-borne
virulence factors and the presence of fecal
cytokines. The different patterns of
virulence factors of EAEC revealed several clusters demonstrating diversity among the isolates from the various regions.