CXCL9 and staphylococcal pneumonia: The capacity of the prediction model based on serum levels of CXCL9 and CXCL10 to discriminate between pneumococcal and staphylococcal pneumonia was validated in an independent cohort of 20 mice infected with S. aureus and 16 mice infected with S. pneumoniae from a different genetic background (C57BL/6) and comprising 50% males and 50% females.