The effect of linezolid on the phagocytic and bactericidal functions of human polymorphonuclear neutrophils (PMN) against gram-positive cocci was evaluated. Preincubation (30 min; 37 degrees C) of PMN with different concentrations of linezolid (2, 10 and 20 mg/l) did not significantly affect the phagocytosis of either Staphylococcus aureus (methicillin susceptible and resistant) or Enterococcus faecalis (vancomycin susceptible and resistant). Overnight exposure of vancomycin-resistant E. faecalis to 1/4 minimum inhibitory concentrations (MIC) of linezolid slightly increased phagocytosis by PMN. Preincubation of the other three strains with 1/4 MIC of linezolid did not affect phagocytosis by these cells. Preincubation of PMN (30 min; 37 degrees C) using different extracellular concentrations of linezolid (2, 10 and 20 mg/l) did not affect their production of either superoxide or hydrogen peroxide radicals. In conclusion, linezolid did not affect the phagocytic and bactericidal functions of human PMN.
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