It is interesting to note that previous studies by Bannerman and co-workers, as well as Yang and co-workers, had demonstrated that while the Gram negative mastitis-causing pathogen E. coli elicited increases in IL-8 expression, perhaps the most common mastitis-causing pathogen, S. aureus, failed to trigger such an effect (Bannerman et al., 2004; Yang et al., 2008). This evidence concerns the gene CXCL8 and mastitis.