Predictors of mortality in Staphylococcus aureus infections: The role of C-reactive protein, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio

Objective Staphylococcus aureus causes infections ranging from mild skin conditions to life-threatening diseases such as endocarditis. The incidence of S. aureus infections is increasing due to the rise in invasive procedures and immunosuppression. Inflammatory markers such as C-reactive protein level, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio are useful for monitoring disease severity. This study aimed to identify the clinical and laboratory predictors of mortality in patients with S. aureus infections. Methods This retrospective observational study included patients aged >18 years with S. aureus growth who were treated at a tertiary hospital between 1 November 2013 and 1 February 2022. Infections were classified as pneumonia or infections of the bloodstream, bone and joint, and skin and soft tissue. Results Univariate analysis revealed that age >73 years, emergency department admission, and methicillin resistance were significant mortality risk factors. Multivariate analysis showed that age >73 years, pneumonia, and C-reactive protein level >86 mg/L increased the mortality rate by 3.5-, 7.6-, and 4.4-fold, respectively. Conclusion C-reactive protein level, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio are accessible, cost-effective markers that aid in predicting mortality. Integrating these biomarkers with clinical parameters such as advanced age and pneumonia can improve early risk stratification in patients with S. aureus infections.