Electrophoretic mobility of cefodizime-treated Staphylococcus aureus and chemiluminescence of human polymorphonuclear...

The electrophoretic mobility of Staphylococcus aureus 209P treated with cefodizime or cefotiam was examined by microscopic electrophoresis, and the production of oxygen-derived radicals by human polymorphonuclear leucocytes (PMN) was measured by a luminol-chemiluminescence assay. S. aureus cells moved from the negative to the positive electrode. Treatment with more than 0.039 mg/L (1/256 MIC) cefodizime or 0.313 mg/L (1/4 MIC) cefotiam significantly reduced the mean mobility compared with the untreated bacterial cells. The decrease of the electrophoretic mobility of antibiotic treated bacteria indicated the decrease of the negative charge of the cell surface. Chemiluminescence of PMN when stimulated by S. aureus treated with more than 0.156 mg/L cefodizime (1/64 MIC) or 1.25 mg/L cefotiam (MIC) increased significantly compared with the untreated cells. These results suggested that the antibiotics caused a decrease of negative charge density on the cell surface of S. aureus, followed by an increase of phagocytic activity of PMN for S. aureus. Furthermore, cefodizime showed this effect even at the low drug-concentration which did not influence the growth of the bacteria cells.