P914 An adult zebrafish model for adherent-invasive Escherichia coli indicates protection from infection by treatment with probiotic E. coli Nissle

Abstract Background Adherent-invasive Escherichia coli (AIEC) is an opportunistic pathogen associated with major inflammatory bowel disease (IBD), Crohn’s disease (CD) and ulcerative colitis (UC). AIEC is a human commensal but during unfavorable gastric conditions it exhibits pathogenic properties and induces inflammation in the gut, sometimes progressing to inflammation-induced colon cancer. The exact mechanisms for AIEC pathogenesis are still being discovered. As a human opportunistic pathogen, AIEC has few animal models. In recent years, zebrafish have emerged as a useful model for studies of various human pathogens. Here, a zebrafish model to study AIEC infection was developed. Methods Colonization of AIEC from overnight culture was determined with different infectious doses (103, 104, 105 and 106 CFU/ml of infection water) in zebrafish, incubating fish with AIEC in water for 6 h and then in fresh water for 18 h at 28o C. The invasive property of AIEC in zebrafish gut was determine by gentamycin protection assay. Persistent colonization of AIEC in zebrafish gut was also assessed for 10 days. Induction of pro-inflammatory markers such as IL-1β, TNFα, IFNγ and S100A-10b (akin to human calprotectin) in zebrafish intestinal cells in response to AIEC infection was determined by qRT PCR and ELISA. A probiotic strain, E. coli Nissle 1917 (EcN) was used as a therapeutic and prophylactic against AIEC infection. Propionic acid was used to augment the AIEC infection and the efficacy of ECN was tested against the hyper-infectious condition of AIEC in zebrafish. Results Bath inoculation with AIEC resulted in colonization, invasion and tissue disruption in the zebrafish intestine. The AIEC infection induced neutrophil recruitment and showed significant pro-inflammatory responses in zebrafish gut. S100A-10b protein of zebrafish, equivalent of a human IBD marker, calprotectin, was significantly increased in the zebrafish gut during AIEC infection. The probiotic E. coli Nissle 1917 (EcN) reduced AIEC colonization, tissue damage and pro-inflammatory responses in zebrafish in both prophylactic and therapeutic ways. Furthermore, EcN diminished the propionic acid-augmented hyper infection of AIEC in the zebrafish model. Conclusion In this study a new zebrafish model was developed to study the infection and inflammation induced by AIEC. Probiotic strain, EcN was used successfully against AIEC to reduce the inflammation in AIEC-zebrafish model.