Amiloride, a diuretic with in vitro antimicrobial activity.

The effect of amiloride, an inhibitor of passive sodium influx in animal cells, was investigated on the in vitro bacterial growth. Amiloride blocked the growth of different bacterial strains at concentrations ranging from 25 to 1,300 micrograms/ml. While generally the block was bacteriostatic and bacteria, on amiloride removal, recovered their ability to growth, the drug showed a killing activity on hemolytic streptococci. Gram-positive bacteria revealed a greater susceptibility to amiloride than gram-negative ones. Although an hitherto unknown effect of amiloride cannot be excluded, from the known mechanism of action of amiloride on animal cells it might be suggested that sodium permeability plays a critical role on bacterial multiplication.