CXCL9 and Sepsis: Because the results of our study in the murine system indicate that serum levels of CXCL9 and CXCL10 can discriminate between S. pneumoniae and S. aureus pneumonia, these chemokines may be used as surrogate biomarkers to increase the diagnostic power of PCT and justify future studies to validate their utility as pathogen-specific biomarkers in humans with CAP, and perhaps other invasive infections due to S. pneumoniae such as sepsis or CNS infections.