Mücke MM, Mayer A, Kessel J, et al. - Researchers here examined whether fluoroquinolone-based spontaneous bacterial peritonitis (SBP) prophylaxis is effective in an era and area of frequent antibiotic resistance. In this prospective observational study, they recruited and followed patients with liver cirrhosis and an indication for fluoroquinolone-based prophylaxis of SBP in a large German tertiary reference center. Comprehensive microbiological and clinical monitoring were performed at baseline and after 30, 60, 90, and 180 days of prophylaxis. Antibiotic prophylaxis was provided to 77 patients for an average of 93 days. Colonization with multidrug-resistant organisms (MDROs) was reported in high number of these patients at baseline (N = 39, 50.6%). Observations revealed less effectiveness of antibiotic prophylaxis of SBP in patients with known MDROs. Regular MDRO screening appears to be valuable to tailor therapy of secondary infections and re-appraise antibiotic prophylaxis in case of selection of quinolone resistance.