General Phenotype of NADase Induction by CLI Treatment in Streptococcus pyogenes

Figure 1

Extracellular NADase activity in emm1-type strains cultured with clindamycin (CLI). One unit of NADase activity was defined as the amount (μg) of β-NAD cleaved per hour per μL of culture supernatant, as described previously [10]. The OD₆₆₀ of overnight culture with CLI (2⁻⁸ to 2⁻⁴ μg/ml) is shown by a percentage (%) of that without CLI (0 μg/ml). The maximum CLI concentration that did not suppress the bacterial growth to less than 50% of that without CLI is shown in red, which was 2⁻⁶ μg/ml in strains 1529, 11T-3, 10–85, and 11–171, and 2⁻⁵ μg/ml in strain 12–5. At least three independent experiments were performed. Error bars indicate the standard errors of the means. Significant increases in extracellular NADase activity by CLI treatment when compared with that without CLI treatment, shown by the black bar, are marked with asterisks ( using Student’s t-test).