HETEROGENEITY OF ENTEROAGGREGATIVE ESCHERICHIA-COLI VIRULENCE DEMONSTRATED IN VOLUNTEERS

Enteroaggregative Escherichia coli (EAggEC) are diarrheal pathogens de fined by aggregative adherence to HEp-2 cells. In an effort to identif y pathogenic EAggEC isolates, four groups of 5 volunteers were fed 1 o f 4 different EAggEC strains, each at a dose of 10(10) cfu, Strain 042 caused diarrhea in 3 of 5 adults; 3 other EAggEC isolates (17-2, 34b, and JM221) failed to elicit diarrhea. A gene encoding enterotoxin EAS T1 was found in strains 042 and 17-2 but not 34b or JM221; a 108-kDa c ytotoxin was expressed in all 4 isolates. All 4 isolates showed a mode st degree of gentamicin protection in HEp-2 cells. 17-2, 34b, and JM22 1 expressed the fimbrial antigen AAF/I; 042 did not express this fimbr ia as determined by immunogold electron microscopy and genetic probe h ybridization.