Serum Antibody Responses to Bacterial Enteropathogens in Swedish Travellers to South-East Asia

The possibility that serological analysis may be more sensitive than bacteriological examinations of stool samples to detect enteric infections was evaluated in 80 Swedish travellers to South-East Asia. Serum and faecal specimens were collected before, during and after their travel. Serological analyses of pre-travel and any later serum specimen identified infection with enterotoxinogenic Escherichia coli (ETEC), Salmonella or Campylobacter jejuni in 28% of the travellers. The seroconversion rate was 72% in travellers excreting the homologous pathogen in their stool; all symptomatic cases and half of those who had an asymptomatic infection seroconverted. Bacteriological examinations of stool samples collected repeatedly during travel identified an enteropathogen in 20% of the travellers. However, the isolation rate decreased to 11%, when only a single routine faecal specimen was examined. Our findings suggest that serological analyses of pre- and post-travel specimens are sufficiently specific and may be at least as sensitive as conventional bacteriology to identify infections with bacterial enteropathogens in travellers. However, reliable serodiagnosis requires collection of pre-travel sera and might therefore only be useful in prospective studies of travellers' diarrhoea.