CP-negative S. aureus strains are frequently isolated from patients with osteomyelitis, mastitis, or cystic fibrosis, providing evidence that the loss of CP expression (due to mutations in any of the genes essential for CP biosynthesis or in the promoter region; Cocchiaro et al., 2006; Tuchscherr et al., 2010) may be advantageous for S. aureus during chronic infection (Herbert et al., 1997; Lattar et al., 2009; Tuchscherr et al., 2010). This evidence concerns the gene CP and mastitis.