BACKGROUND: Ileal lesions of Crohn's disease (CD) patients are colonized by adherent-invasive Escherichia coli (AIEC) able to survive in macrophage cell lines. We analyzed the ability of monocyte-derived macrophages (MDM) from CD patients to control AIEC intracellular replication and the pro-inflammatory cytokine response of the infected-MDM. METHODS: Peripheral blood MDM were obtained from 24 CD genotyped for NOD2 and ATG16L1 mutations, 5 ulcerative colitis (UC) patients and 12 healthy controls (HC). The numbers of intracellular bacteria were determined using gentamicin assay. Cytokine secretion was quantified by ELISA. RESULTS: We observed that higher levels of bacteria were internalized within MDM from CD patients than MDM from HC or UC patients. MDM from CD patients were unable to restrict AIEC intracellular replication. Infection of MDM from CD patients with AIEC resulted in significantly increased secretion of IL-6 and TNF-alpha than infection with non-pathogenic E. coli. AIEC-infected MDM from CD patients exhibited a disordered cytokines secretion compared to MDM from UC patients and HC. AIEC-infected MDM from patients with quiescent CD released significantly higher amounts of IL-6 and TNF-alpha than those with active disease or those from HC. The level of secreted TNF-alpha was correlated to the number of intracellular AIEC in MDM from CD patients. Treatment of MDM with infliximab did not change the MDM behaviour. CONCLUSION: MDM from CD patients are unable to restrict intracellular AIEC replication, leading to disordered inflammatory response influenced by disease activity.