The impact of a penicillin allergy label on antibiotic resistance in patients with bloodstream infections: Study Protocol [version 1; peer review: 2 approved]

Background Antibiotics used in place of penicillin antibiotics in patients with penicillin allergy may have a greater tendency to select for antimicrobial resistance (AMR). Therefore, patients with penicillin allergy may be at an increased risk of AMR bloodstream infections, which are associated with significant morbidity and mortality and are increasing in prevalence. This study aims to investigate whether patients with a penicillin allergy have a higher risk of AMR bloodstream infections. Methods This is an observational cohort study using routinely collected patient level data obtained from the Health Data Research UK acute care hub ‘PIONEER’. The study will include adult patients (≥16 years old) admitted to the University Hospital Birmingham NHS Trust between 2015 and 2019 who had positive blood cultures during their admission. The primary outcome of interest is the presence of an AMR bloodstream infection (BSI). Associations between the primary outcome and penicillin allergy status will be investigated using multivariable logistic regression. Secondary outcomes will include rates of community and hospital acquired AMR BSIs, BSIs caused by pathogens resistant to one or more key antibiotics or antibiotic classes, total antibiotic use, length of hospitalisation and mortality rates.