Figure 8.

Acquisition of resistance by the treatment of AZB and erythromycin against S. aureus ATCC 25923 cells after multiple passages of growth. The fold change of minimum lethal concentration (MLC) (MLC_i+1/_i, where i is the passage of growth from 1 to 9) for AZB and erythromycin with the pressure of their sub-lethal concentration (0.5 MLC) was regarded as the indicator for the development of drug resistance. The inset displays the enlarged region including passages 1–7. Experiments were performed in triplicates and showed the same results in all experiments. The values are also indicated in Table 1.