Gene clusters governing the production of hemolysin and mannose-resistant hemagglutination are closely linked in Escherichia coli serotype O4 and O6 isolates from urinary tract infections.

The genes encoding alpha-hemolysin and mannose-resistant hemagglutination were shown to be closely linked in cloned DNA from two Escherichia coli urinary tract isolates of serotypes O4 (J96) and O6 (C1212). DNA hybridization experiments demonstrated that the hly and mrh gene clusters of other E. coli O6 serotypes were also linked. Colony hybridizations showed that most normal fecal E. coli do not contain hly and mrh DNA but much of the intervening DNA between these two gene clusters is common among all E. coli. We have further demonstrated that there is a small (about 1 kilobase) region of homology located on both sides of the hly sequence and present elsewhere in the C1212 strain. We suggest that linkage of hly and mrh occurred through a transposition event, and we discuss the potential significance of this linkage in the acquisition of virulence determinants by these bacteria.