Genetic background of Escherichia coli isolates from peritoneal dialysis patients with peritonitis and uninfected control subjects.

Escherichia coli is the most common cause of Gram-negative peritonitis resulting in peritoneal function deterioration as well as poor clinical outcome in continuous ambulatory peritoneal dialysis (PD) patients. In this study, we analyzed the phylogenetic background and genetic profile of the E. coli isolates and sought to determine the characteristics of specific bacteria associated with peritonitis. E. coli isolates from 56 episodes of peritonitis in 46 PD patient cases and rectal isolates from 57 matched PD control patient cases were compared for both phylogenetic groups and the presence of virulence factors (VFs). There were no significant differences in terms of demographic data between the peritonitis and control groups. Peritonitis isolates exhibited a significantly greater prevalence of 8 VFs. In multivariate logistic regression analysis, kpsMT II (group 2 capsule synthesis) was the strongest VF predictor of peritonitis (OR = 8.02; 95%CI = 3.18-20.25; P < 0.001), followed by traT (serum-resistance-associated outer membrane protein) (OR = 3.83; 95%CI = 1.33-11.03; P = 0.013). The pathogenic groups of E. coli contained a higher concentration of individual VFs compared to the commensal groups. The prevalence of pathogenic E. coli was much higher in peritoneal isolates than rectal isolates (64.3 vs 31.6%, P = 0.001). Our results indicate that the E. coli peritonitis and rectal isolates are different in PD patients. The specific VFs associated with peritonitis isolates may directly contribute to the pathogenesis of peritonitis.