Chromosomal deletions and rearrangements cause coordinate loss of haemolysis, fimbriation and serum resistance in a uropathogenic strain of Escherichia coli.

The coincidence of virulence factors such as haemolysin, adhesins and 0 · and K antigens among strains of Escherichia coli causing urinary tract infections (UTI) is well-documented.-4 lndeed it seems that prominent uropathogenic strains belang to a restricted number of clonal types possessing specific constellations of these chromosomally-encoded characters and that such associations frequently reflect a close genetic linkage of virulence genes.8 By assessing the serum sensitivity of spontaneaus non-haemolytic mutants arising from chromosomal deletions in a haemolytic serum resistant uropathogenic strain, we are able to suggest that the strong correlation between haemolysis and high Ieveis of serum resistance among urinary isolates may have a similar genetic basis.