sentence: Detection of capsule in vivo expression is shown for representative CC8-t008 ( USA300 ) and CC8-t064 ( USA500 ) isolates in Fig 4A.To assess whether the observed in vivo expression was due to either mutations reverting in vivo or contamination by other S. aureus that are capsule producers , mice ( two mice per bacterial strain tested ) were challenged individually with three USA300 strains ( PFESA0119 , PFESA0029 and PFESASA0021 ) and Reynolds strain .