RT Journal Article SR Electronic T1 Protocol for a double-blind placebo-controlled trial to evaluate the efficacy of probiotics in reducing antibiotics for infection in care home residents: the Probiotics to Reduce Infections iN CarE home reSidentS (PRINCESS) trial JF BMJ Open JO BMJ Open FD British Medical Journal Publishing Group SP e027513 DO 10.1136/bmjopen-2018-027513 VO 9 IS 6 A1 Eleri Owen-Jones A1 Rachel Lowe A1 Mark Lown A1 David Gillespie A1 Katy Addison A1 Tony Bayer A1 Philip C Calder A1 Jane Davies A1 Mina Davoudianfar A1 James Downs A1 Alison Edwards A1 Nick A Francis A1 Richard Fuller A1 Richard Hobbs A1 Kerenza Hood A1 Mandy Lau A1 Paul Little A1 Michael Moore A1 Victoria Shepherd A1 Helen Stanton A1 Alun Toghill A1 Mandy Wootton A1 Chris C Butler YR 2019 UL http://bmjopen.bmj.com/content/9/6/e027513.abstract AB Introduction Care home residents are at increased risk of infections and antibiotic prescription. Reduced antibiotic use from fewer infections would improve quality of life. The Probiotics to Reduce Infections iN CarE home reSidentS (PRINCESS) trial aims to determine the efficacy and investigate mechanisms of daily probiotics on antibiotic use and incidence of infections in care home residents.Methods and analysis PRINCESS is a double-blind, individually randomised, placebo-controlled trial that will assess the effect of a daily oral probiotic combination of Lactobacillus rhamnosus, GG (LGG) and Bifidobacterium animalis subsp. lactis, BB-12 (BB-12) on cumulative antibiotic administration days (CAADs) (primary outcome) for infection in up to 330 care home residents aged ≥65 years over up to 12 months. Secondary outcomes include: Infection: Total number of days of antibiotic administration for each infection type (respiratory tract infection, urinary tract infection, gastrointestinal infection, unexplained fever and other); number, site, duration of infection; estimation of incidence and duration of diarrhoea and antibiotic-associated diarrhoea; Stool microbiology: Clostridium difficile infection; Gram-negative Enterobacteriaceae and vancomycin-resistant enterococci; LGG and BB-12. Oral microbiology: Candida spp. Health and well-being: Self and/or proxy health-related quality of life EQ5D (5 L); self-and/or proxy-reported ICEpop CAPability measure for older people. Hospitalisations: number and duration of all-cause hospital stays. Mortality: deaths. Mechanistic immunology outcomes: influenza vaccine efficacy (haemagglutination inhibition assay and antibody titres); full blood count and immune cell phenotypes, plasma cytokines and chemokines; cytokine and chemokine response in whole blood stimulated ex vivo by toll-like receptor 2 and 4 agonists; monocyte and neutrophil phagocytosis of Escherichia coli; serum vitamin D.Ethics and dissemination Ethics approval is from the Wales Research Ethics Committee 3. Findings will be disseminated through peer-reviewed journals and conferences; results will be of interest to patient and policy stakeholders.Trial registration number ISRCTN16392920; Pre-results.