Phagocytic activity of polymorphonuclear leukocytes on Escherichia coli previously exposed to metronidazole.

A study was made of the action of different concentrations of metronidazole of the viability of Escherichia coli under aerobic and anaerobic conditions. The viability of E. coli was reduced by 60 to 99% after 24 hours of anaerobic incubation, according to the concentration of metronidazole tested. In addition, there were significant morphological changes in the bacteria. Exposure of antibiotic-induced filaments of E. coli LP 136 to phagocytosis caused the cfu/ml value to drop by 60% after 120 minutes. Under identical conditions, using the mutant strain E. coli RYC 819, which did not become filamented by metronidazole although it did present similar ultrastructural changes, this reduction reached 83%. These results may explain the therapeutic success of metronidazole in polymicrobial infections.