A prospective study of serum antibody responses to enterotoxinogenic Escherichia coli in Swedish travellers.

Serological responses to relevant enterotoxinogenic Escherichia coli (ETEC) antigens were studied in 85 Swedish travellers to subtropical and tropical areas. Serum samples were collected from the travellers before and then after 3-5 weeks, i.e. within a week after return to Sweden, when a faecal specimen was also taken. 40% of the participants had traveller's diarrhoea during their visit abroad, while 21% reported "loose stools" and 39% had no such problems. ETEC was rarely isolated from the stool of any of the travellers on their return to Sweden (6%). Salmonellae, Shigellae or Campylobacter jejuni were isolated from 13 (15%) of the travellers, 12 of whom were healthy when the specimens were collected and 4 of whom had been healthy during travel as well. Significant serum antibody responses to E. coli heat-labile enterotoxin (LT) and colonization factor antigens CFA I or II were seen in 33% and 20% of the travellers, respectively. Anti-LT responses were comparable in participants with traveller's diarrhoea or "loose stools" and in the healthy ones, whereas anti-CFA responses were more frequent in those with symptomatic infections. Of 34 Swedes in a non-travelling control group none responded to LT and one to CFA I or CFA II.