Probiotics are used by people with cystic fibrosis (CF) and other chronic diseases to manage gastrointestinal symptoms. To describe probiotic knowledge; its relationship with probiotic use, probiotic information sources and factors influencing choice in adults with CF and a general population control group. A cross-sectional questionnaire study was conducted in adults with CF (n = 205) and Controls (n = 158). Probiotic knowledge was compared between CF and Controls using a knowledge score (maximum 5) based on predefined criteria: (1a) bacteria/microorganism; (1b) live; (2a) administered; (2b) adequate dose and (3) health benefit, using independent samples t-test. Two-way analysis of variance explored knowledge scores between CF and Control and between and groups. Chi-square and Fisher's exact tests compared knowledge criterion, probiotic sources and influences on probiotic choice between groups. Thematic analysis of open-text responses explored probiotic-related knowledge and influences on probiotic decision making. Knowledge scores (mean ± SD) did not differ between CF (1.70 ± 1.12) and Controls (1.89 ± 0.99), = 0.13. Probiotic use was associated with knowledge score ( < 0.001). More CF than correctly identified criteria 1a (65% vs. 38%), 1b (16% vs. 0%), 2a (45% vs. 22%) and 3 (73% vs. 42%) (all < 0.005). CF participants considered 'dairy yoghurt' (69%), 'live cultures' (64%) and 'fermented foods' (37%) as 'all/mostly' probiotic sources. The internet was the commonest source of probiotic-related information. Probiotic knowledge and use were associated in adults with CF. Understanding of probiotic characteristics and sources were limited. Education is needed to help guide patient probiotic decision making.
