Brain infections, such as bacterial meningitis, still cause death and disability in the UK and worldwide. The key decision for a doctor is to decide whether a patient has bacterial meningitis, or whether they have a similar condition (a clinical mimic), such as viral meningitis. In both cases the patient often looks the same. However, bacterial infection needs immediate treatment with antibiotics whereas a mimic does not. The essential test for distinguishing between the two is the lumbar puncture (a needle passing between the bones in the spine). The lumbar puncture is often delayed, or not performed at all. This can result in delayed antibiotic treatment for those who need it, or unnecessary antibiotics in those who do not, as well as a patient not receiving a diagnosis. We offer a novel test measuring the body's response to bacterial infection in the blood. This means patients can be tested without having to wait for the lumbar puncture. We believe this test will help doctors to more accurately decide which patients do or do not need antibiotics. This will promote appropriate treatment, reduce unnecessary antibiotics, reduce inpatient stay, improve patient care and reduce the burden on health staff and hospitals. We are working with an industrial company who are experts in developing diagnostic tests, to develop our test for clinical use. We are also linking with many expert clinical teams in the UK, Europe, Brazil and Africa to assess our test on a large number of patients to ensure it is accurate. Through this project we will confirm the test is accurate and refine the test so that it can be used in hospitals in under the next 5 years.The purpose of the TRIM study of UK Meningitis is to develop a novel blood test that can diagnose bacterial meningitis by looking at the expressed RNA of the patient's immune system. Bacterial meningitis represents the most critical patient group within all cases of suspected meningitis and thus there is a critical need to determine the need for antibiotics and more intensive care. When available, this test can be used to rapidly rule in, or out, the need for antibiotic therapy much faster than an LP can be performed. Routinely collected standard of care date, surplus Cerebral Spinal Fluid, and the additional blood sample will be used to validate the TRIM test's diagnostic accuracy.