FIG 8 .

METH reduces human neutrophil phagocytosis, respiratory burst, and killing of S. aureus. (A) Phagocytosis (percentage) of FITC-labeled S. aureus clinical strains (n = 6) by human neutrophils was determined using FACS analysis after a 60-min incubation with METH. (B) Killing of S. aureus by neutrophils was determined from CFU counts. For panels A and B, dashed lines and error bars represent the averages and standard deviation of six measurements (each symbol represents a single strain). Significance (P < 0.05) was calculated by an ANOVA and adjusted by use of the Bonferroni correction. For panel A, *, #, and & indicate a lower phagocytosis percentage than in untreated, 25 µM Chlq, or 25 µM METH groups, respectively. For panel B, ϕ, χ, @, and $ indicate a higher survival percentage than in untreated, 25 µM Chlq, 25 µM METH, and 50 µM METH groups, respectively. (C) Oxidative burst was quantified for 60 min based on luminol chemiluminescence after untreated or Chlq-, CytD-, or METH-treated neutrophils were coincubated with MRSA strain 6498. Untreated and uninfected neutrophils were also used as controls. Symbols and error bars denote means and standard deviations. Significance (P < 0.05) was calculated by an ANOVA and adjusted by use of the Bonferroni correction at each time point. This experiment was performed twice and similar results were obtained. The results shown are representative of an individual experiment.