Association between cell-bound haemolysin and cell-detaching activity of Escherichia coli isolated from children

Haemolysin alpha (HlyA) produced by cell-detaching Escherichia coli, a putative new class of enteric pathogen, is considered to be the main factor responsible for detachment of cells cultured in vitro. HlyA is one of the few E. coli proteins actively secreted into the medium during exponential growth. In the present study 27 HlyA-positive E. coli isolates, randomly selected from stool specimens, produced a cell-bound haemolysin that was detectable during the exponential and stationary growth phases. The influence of both cell-free and cell-bound haemolysins of the selected isolates on cell-detaching activity of E. coli in vitro was determined. The results suggest that cell-bound haemolysin rather than cell-free HlyA was responsible for the cell-detaching activity of E. coli strains tested.