Sensitivity to paraquat of two S. epidermidis strains. The bacteria were cultured in MH broth (OXOID) with different concentration of paraquat (from 1 mM to 8 mM) and incubated at 35°C for 16–20 h. The MIC was defined as the lowest concentration of paraquat giving complete inhibition of visible growth. The growth of bacteria incubated with lower concentration paraquat than MIC was measured by OD600. The bar graph represents the average of three independent experiments, with standard deviations denoted by the error bars. *, P < 0.01.