Figure 1.

PtpA promotes S. aureus survival in macrophages. A, S. aureus short-term survival in infected macrophages. Cells of S. aureus strains SA564 and Newman and their isogenic ΔptpA mutants and cis-complemented derivatives, respectively, were used to infect RAW 264.7 macrophages (5 × 10⁵ cells/ml) at a m.o.i. of 20 for 1 h at 37 °C followed by 30 min incubation with gentamicin. Macrophages were then incubated for 45 min in complete media supplemented with lysostaphin to kill extracellular bacteria that might be released from lysed macrophages during the successive incubation time, and subsequently lysed in 0.1% Triton X-100. Survival rates are given in relationship to the intracellular bacterial cell numbers seen pGt treatment. Results represent the mean ± S.D. (n = 5). *, p < 0.05; NS, not significant (Mann-Whitney-U test). B, S. aureus long-term survival in infected macrophages. RAW 264.7 macrophages (5 × 10⁵ cells/ml) were infected with a m.o.i. of 20 of S. aureus strains Newman (black bar), Newman ΔptpA (white bar), and Newman ΔptpA::ptpA_Flag (gray bar), respectively, and co-incubated for 2 h at 37 °C, followed by a gentamicin/lysostaphin treatment to eliminate external bacteria. Macrophages were lysed with Triton X-100 (0.1%) at 22 h pGt, and bacteria enumerated by plate counting. Survival rates are given in relationship to the intracellular bacterial cell numbers seen immediately after gentamicin treatment. Data represent the mean ± S.D. (n = 5). *, p < 0.05; NS, not significant (Mann-Whitney-U test). C, in vitro growth kinetics of the S. aureus Newman/ΔptpA/ΔptpA::ptpA_Flag strain triplet. Growth of S. aureus strains Newman (black symbols), Newman ΔptpA (white symbols), and Newman ΔptpA::ptpA_Flag (gray symbols) was measured in TSB at 37 °C and 150 rpm. Data represent the mean A₆₀₀ readings at the time points indicated (n = 3).