Natural history of enteroaggregative and enterotoxigenic Escherichia coli infection among US travelers to Guadalajara, Mexico.

The natural history of enteroaggregative Escherichia coli (EAEC) and enterotoxigenic E. coli (ETEC) infection was studied among 40 US travelers who provided weekly stool samples for 4 weeks after arrival in Mexico. At enrollment, 5 subjects were colonized by EAEC and 3 by ETEC. During the first 2 weeks after enrollment, 12 developed EAEC diarrhea, 7 developed ETEC diarrhea (5 with mixed EAEC/ETEC diarrhea), 13 had EAEC colonization, and 7 had ETEC colonization. During the third and fourth weeks, 4 experienced EAEC diarrhea, 2 experienced ETEC diarrhea (1 with mixed EAEC/ETEC diarrhea), 31 had EAEC colonization, and none had ETEC colonization. Plasmid DNA analysis showed a high degree of heterogeneity among EAEC isolates. Symptomatic EAEC infection occurred early after arrival in Guadalajara, Mexico, and was as common as ETEC infection. Asymptomatic EAEC infection was recurrent.