Role of immunosuppression in the development of quinolone-resistant Escherichia coli spontaneous bacterial peritonitis and in the mortality of E. coli spontaneous bacterial peritonitis

Background: Norfloxacin decreases the incidence of spontaneous bacterial peritonitis in cirrhotics, but promotes the appearance of quinolone-resistant Escherichia coli. Aim: To define the characteristics of quinolone-resistant E. coli spontaneous bacterial peritonitis. Methods: E. coli-positive ascitic fluid cultures were identified during a 6-year period. Data on quinolone-sensitive and quinolone-resistant E. coli spontaneous bacterial peritonitis were compared. Results: One hundred and two E. coli-positive ascitic fluid cultures were detected. Cirrhotics accounted for 67 cases. Spontaneous bacterial peritonitis was found in 47 of the 67 (70%) cases [35 (74%) caused by quinolone-sensitive and 12 (26%) caused by quinolone-resistant E. coli]. Norfloxacin prophylaxis was higher in the quinolone-resistant group (92% vs. 6%, P < 0.001). Compared with patients with quinolone-sensitive E. coli spontaneous bacterial peritonitis, those with quinolone-resistant E. coli spontaneous bacterial peritonitis showed a higher prevalence of associated immunosuppressive factors (immunosuppressive drugs, human immunodeficiency virus infection or cancer) (92% vs. 20%, P < 0.001). Steroid therapy was independently associated with quinolone-resistant E. coli spontaneous bacterial peritonitis (odds ratio, 49; 95% confidence interval, 3.4-699; P = 0.004). The Child-Pugh score (P = 0.03), immunosuppression (P = 0.02) and renal failure (P = 0.01) were independent predictors of E. coli spontaneous bacterial peritonitis-related mortality. Conclusions: Associated immunosuppression is an important co-factor for the development of quinolone-resistant E. coli spontaneous bacterial peritonitis and for E. coli spontaneous bacterial peritonitis-related mortality.