Predictive factors of outcome following nonfermenting gram-negative bacilli peritonitis in peritoneal dialysis

Background Peritonitis due to gram-negative bacilli (GNB), particularly nonfermenting GNB (NF-GNB), is a serious complication of peritoneal dialysis (PD) with a low resolution rate. Beyond the patient’s condition, microbiological properties such as antimicrobial resistance, biofilms and the production of other virulence factors can explain the bad outcomes. This study aimed to evaluate the influence of the patient’s condition, the microbiological characteristics, including biofilm production, and the treatment of peritonitis on peritonitis resolution.Methods We reviewed the records of 62 new peritonitis episodes caused by NF-GNB that occurred between 1997 and 2015 at a single university center. The influence of microbiological and clinical factors on resolution chance was analyzed by logistic regression.Results The etiologies were species of Pseudomonas (51.6%), Acinetobacter (32.2%), and others (16.1%). There was a high (72.9%) proportion of biofilm producers’ lineages. The in vitro susceptibility rate of Pseudomonas spp. to amikacin, ciprofloxacin, and ceftazidime was significantly greater than that of Acinetobacter spp. and other species; however, there was a similar low resolution rate (<45%) among the episodes attributable to Pseudomonas spp, Acinetobacter spp, and other NF-GNB. Pre-existent exit-site infection was independently associated with nonresolution. No other factor, including biofilm production, was associated with the outcome. Conclusions Peritonitis due to NF-GNB in PD is a severe infection with a reduced resolution rate, and pre-existent exit site infection negatively influences the chance of resolution. The higher in vitro susceptibility of Pseudomonas compared to that of other NF-GNB with a similar resolution rate, suggests bacterial virulence factors beyond biofilm and can act in concert, thereby worsening the outcome.