Investigation of an outbreak of Campylobacter upsaliensis in day care centers in Brussels: analysis of relationships among isolates by phenotypic and genotypic typing methods.

An outbreak of Campylobacter upsaliensis in four Brussels day care centers (A, B-1, B-2, and C) affected 44 children. Diarrhea was the major symptom. From January 1991 to June 1992, the outbreak strain was isolated from 3, 1, and 21 (of 68) children in centers A, B-1, and B-2, respectively, and from 19 of 22 children in center C, IgG, IgM, and IgA antibodies were detected by Western blotting of serum specimens of 9 of 10 and 13 of 16 children in centers B-2 and C, respectively. Strains were typed by biotyping, DNA restriction-based and antibiotic susceptibility typing, whole cell protein and plasmid analysis, restriction fragment length polymorphism (RFLP), and polymerase chain reaction (PCR). On the basis of RFLP and PCR typing, the strains could be divided into two strongly related clonal variants: One was isolated only from the children of center A and the second only from children in the other day care centers.