Prospective study of Campylobacter jejuni infection in Chilean infants evaluated by culture and serology.

A prospective study of Campylobacter jejuni infection was performed during a 6-month period in a cohort of 198 Chilean infants. Surveillance was based on biweekly home visits by a team of trained nurses. C. jejuni colonization was studied by culturing stool samples from diarrheal episodes and paired asymptomatic controls and by performing an enzyme-linked immunosorbent assay developed to measure C. jejuni outer membrane protein polyvalent antibodies in a representative group of infants. C. jejuni was isolated from 30 of 299 diarrheal episodes (10%) and from 17 of 304 samples from asymptomatic infants (6%). Significantly higher (P less than 0.05) C. jejuni illness/infection ratios were found in infants less than 9 months old. Polyvalent antibodies to C. jejuni were found in 27 of 89 serum samples (30%). The lowest prevalence (4%) was observed among infants less than 9 months old, and the highest was found in patients older than 15 months (63%; P less than 0.01). Data obtained by analysis of paired serum samples revealed a significant increase in the number of seropositive individuals, from 8% on admission to 50% at the end of the protocol (P less than 0.001). The change in the immune status of these infants was associated with symptomatic infection in 9 of 18 cases. The antibody rise found in the remaining nine infants suggested the presence of asymptomatic C. jejuni infections. This inference was documented by the isolation of C. jejuni from stools of two of these infants when the infants were randomly studied while asymptomatic. This study points out the impact of C. jejuni-associated diarrheal episodes and the high frequency with which asymptomatic infections elicit specific antibodies in infants living in areas such as Chile.