STRUCTURE AND FUNCTION OF PLASMID PCOLD157 OF ENTEROHEMORRHAGIC ESCHERICHIA-COLI O157 AND ITS DISTRIBUTION AMONG STRAINS FROM PATIENTS WITHDIARRHEA AND HEMOLYTIC-UREMIC SYNDROME

In this study, pColD157, a 6.7-kb colicinogenic plasmid of enterohemor rhagic Escherichia coli (EHEC) 0157:H7 strain CL40cu, was characterize d by restriction mapping and determination of its complete nucleotide sequence, The sequence consists of 6,675 bp and shows a high degree of similarity to the nucleotide sequence of colicinogenic plasmids pColD -CA23 and pColK, Seven potential genes were located on pColD157, three of which were closely related (> 97.9%) to the colicin D structural g ene and the corresponding immunity and lysis genes of plasmid pColD-CA 23, and these were therefore designated cda, cdi, and cdl, respectivel y, using the reference extension -CL40 for differentiation, The adjace nt 3' region is related to the origin of replication of pColD-CA23, In contrast, the remaining part of the plasmid harbors a cluster of gene s, closely related to the mobilization genes of pColK, which is follow ed by a 0.3-kb stretch homologous to the pColK resolution function, Th ese determinants were designated mbdA, mbdB, mbdC, and mbdD and cdr, r espectively, Southern blot analysis was performed,vith a probe specifi c for the cda gene of pColD157 and two groups of EHEC 0157:H7 isolates from patients with diarrhea or hemolytic-uremic syndrome resident in Germany. Whereas 16 of 46 E, coli 0157 strains isolated between 1987 a nd 1991 harbored plasmid pColD157, only 1 of 50 strains isolated durin g 1996 carried this plasmid, In addition, all strains harboring plasmi d pColD157 were shown to have colicinogenic activity.