CLONAL ANALYSIS OF ESCHERICHIA-COLI OF SEROGROUPS 09, 020, AND 0101 ISOLATED FROM AUSTRALIAN PIGS WITH NEONATAL DIARRHEA

The genetic diversity of 87 isolates of Escherichia coli recovered fro m Australian pigs with neonatal diarrhea was examined by multilocus en zyme electrophoresis. The isolates were of serogroups O9, O20, and O10 1, and although most isolates lacked K88(F4), K99(F5), 987P(F6), and F 41 fimbriae, they were considered to be involved in the etiology of th e diarrhea. The isolates were extremely diverse, considering their ori gin from a single pathological condition in one country. There were es timated to be 18, 16, and 12 clones of the three respective serogroups in the collection, with serogroup diversities of 0.387, 0.448, and 0. 275, respectively. Comparison with the results previously obtained for isolates from piglets with postweaning diarrhea suggested that bacter ia from piglets with these two conditions did not come from any partic ular common genetic background. The overall genetic diversity for the combined collection was the same as that reported by others for repres entative isolates selected from throughout the species (0.47). The cur rent results indicate that if isolates of these O groups are involved in porcine diarrhea, their pathogenicity is directly linked to their O somatic antigen type and is not simply due to the wide distribution o f a small number of virulent clones.