Yersinia enterocolitica isolated from two cohorts of young children in Santiago, Chile: incidence of and lack of correlation between illness and proposed virulence factors.

Yersinia enterocolitica was isolated from children in two cohorts in Santiago, Chile. In a cohort containing a cross section of children aged 0 to 4 years, Y. enterocolitica was isolated from stool samples of 1.1% of children with diarrhea and 0.2% of age-matched control children. In a subgroup of this cohort from which weekly stool samples were obtained from all children irrespective of clinical status, 6% of children had asymptomatic Yersinia infections. In a birth cohort (with a greater representation of children less than 1 year of age and a significantly higher rate of diarrhea), Y. enterocolitica was isolated from 1.9% of children with diarrhea and 0.6% of controls (P = 0.05). Biogroup 1A strains (which lacked traditional phenotypic and molecular markers for pathogenicity) were isolated from seven children with diarrhea but from no control children in the birth cohort (P = 0.02). All other isolates, including all isolates from asymptomatic children, were "pathogenic" strains in biogroup 4, serogroup O3; no association between these isolates and occurrence of disease was found. Y. enterocolitica is found among young children in Santiago, with asymptomatic infections not uncommon occurrences. However, questions about the association between previously described virulence factors and diarrheal illness remain.