CXCL8 and coinfection: A Wilcoxon comparison was conducted for IL-8 values in cows where the etiological agent of mastitis was identified to be (i) Staphylococcus aureus, (ii) Streptococcus species, (iii) Staphylococcus aureus and Streptococcus species together (co-infection), or (iv) pathogen negative (where there was no etiological agent detected but the cows still presented with mastitis).