Zinc and the heat-labile enterotoxin of Escherichia coli

Enterotoxigenic Escherichia coli is a major cause of diarrhoea in man. When zinc in concentrations of 10(-6) M or 10(-5) M was added to the growth medium, there was a significant increase in heat-labile enterotoxin production by each of six toxigenic strains. Zinc in these concentrations did not alter bacterial growth or the activity of preformed toxin. Other heavy metals did not enhance toxin production and o-phenanthroline, a relatively specific zinc-chelating compound, blocked the enhancing effect. The significance of these findings is discussed in relation to the use of supplemental dietary zinc.