Antimicrobial resistant (AMR) infection is one of the biggest threats to global health. A shocking statistic estimates 10 million deaths globally by 2050 if immediate action is not taken. A dwindling pool of effective antibiotics, coupled with a lack of commercial incentives to develop new antibiotics, has brought us to crisis point. There is an urgent need to develop new approaches to infection management and treatment regimens for AMR organisms. A deeper understanding of pathogen-specific immune dynamics is necessary to facilitate development of new diagnostics and novel vaccines. Improved diagnostics, and prevention of infection in the first place, are key strategies for combatting AMR. Here, we bring together a multidisciplinary team of clinicians, immunologists and data scientists with the goal of defining pathogen-specific immune features predicting onset of and outcomes from bloodstream infection (BSI). We will focus on the primary causative organisms of BSI; Staphylococcus aureus and Escherichia coli. The WHO have identified these as priority pathogens for which AMR is an urgent concern. Patients presenting at the emergency department with symptoms of BSI will be prospectively recruited. In-depth analysis of peripheral leukocyte phenotypes and function will be performed on patients for whom S.aureus or E.coli BSI is confirmed. High-dimensional flow cytometry will characterise leukocytes phenotypes and identify the presence of S.aureus or E.coli specific memory T cells. In vitro assays will address the novel hypothesis that adoption of a cytotoxic phenotype by gdT cells to target intracellular S.aureus or E.coli, is an important predictor of outcome during BSI. Immune features will be correlated with infection type and infection outcomes using advanced statistical and predictive modelling techniques based on machine learning to identity pathogen-specific predictive diagnostic biomarkers and key determinants of BSI outcome. Knowledge gained will enhance infection management and antimicrobial stewardship, ultimately helping turn the tide on AMR infection.