Chryseobacterium meningosepticum usually causes infections in neonates and the immunocompromised. Treatment is handicapped by the organism's inherent multidrug resistance. In this study, the clinical characteristics of patients with C. meningosepticum bloodstream infection (BSI) were retrospectively reviewed. Antimicrobial susceptibilities of the clinical isolates were analysed and their ability to form biofilm was assayed by crystal violet staining and electron microscopy. During 2003-2007, 40 patients with BSI caused by C. meningosepticum were included. Mean patient age was 61.6±22.1 years. Co-morbidities were observed in 38 cases (95.0%) and a high 14-day mortality (52.5%) was observed in these patients. Susceptibility of the isolates was relatively high (>50%) only to piperacillin, piperacillin/tazobactam, trimethoprim/sulfamethoxazole and ciprofloxacin. Multivariate analysis revealed that mortality was associated with the use of central venous catheters, initial inappropriate antimicrobial therapy and higher biofilm production by the organism. Electron microscopy confirmed the formation of biofilm microcolonies on the solid phase of the fibre of nitrocellulose paper in vitro. Time-kill studies showed that biofilm formation helps bacteria to tolerate killing by ciprofloxacin. In conclusion, C. meningosepticum is a biofilm-forming organism. The outcome of patients with biofilm-forming C. meningosepticum infection was adversely affected by the choice of inappropriate antimicrobial therapy and the use of long-term indwelling intravascular catheters. Copyright © 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.