Antibiotic and nonantibiotic ionophores can alter bacterial adherence to mammalian cells

Epithelioid (HeLa) and fibroblastic (L) cells in culture incubated for 18 hr with the ionophores amphotericin B and amiloride were noted to bind significantly more and less bacteria, respectively, than control cells incubated without ionophores. These effects were related to dose and incubation length and were present at concentrations approximating those in vivo after administration of maximal doses of these drugs given to humans therapeutically. Electron microscopy of both receptor cell lines revealed increased length and number of cellular projections in the amphotericin-treated cells and flattening and loss of membrane individuality in the amiloride-treated cells. These findings could explain the differences in subsequent bacterial binding. The ionophores nifedipine and verapamil which block calcium transport in cells which have calcium channels did not alter bacterial binding to these receptor cells or bacterial binding to calcium channel-containing myoblasts (in culture). These data suggest that certain ionophores could alter bacterial colonization and infection in the host indirectly by altering bacterial binding; however, the clinical significance of these findings remains to be determined.