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Fig. 3 N315 Lineage 3 isolates exhibit increased fitness to survive THP-1 macrophage killing. THP-1 macrophages were infected with SH1000 (A?F) and N315 (G?L) parental strains and isolates from passage cycles 4 (P4), 20 (P20), and 32 (P20) from Lineages 1 to 6 after one cycle of THP-1 infection. THP-1 macrophages were infected with S. aureus at MOI 1 for 1 h, gentamicin was added for 72 h, and bacteria were allowed to escape and divide in the macrophage cell culture media prior to a new cycle of infection. New cycle: after 1 h of infection, the media was replaced with media with gentamicin. Bacterial survival was evaluated by comparing bacterial levels after 72 h inside the macrophages to bacterial levels after 1 h of phagocytosis. One-way ANOVA with Holm-Sidak?s multiple comparisons test to Parental. **P < 0.01, ***P < 0.001, ****P < 0.0001.