Increased severity of Escherichia coli peritonitis in peritoneal dialysis patients independent of changes in in vitro antimicrobial susceptibility testing.

OBJECTIVE: Despite improvements in peritoneal dialysis (PD) technique, peritonitis continues to be one of the most frequent complications of PD. Nonresolving peritonitis remains a risk for severe anatomical peritoneal changes that may limit the viability of the membrane for dialysis purposes. We have observed remarkably poor outcome of peritonitis caused by Escherichia coli in the past 6 years. With its very low response rate to broad-spectrum antibiotics, the increased severity of E. coli peritonitis deteriorates peritoneal function and affects patient outcome.

DESIGN: Retrospective study.

SETTING: Two large PD units in two university hospitals.

PATIENTS AND METHODS: The total number of patients reviewed was 456. The records of 49 E. coli peritonitis episodes were studied.The observation period started in 1980 and ended in March 2001. Sixteen males and 19 females were included. Severity was defined in terms of days of peritoneal inflammation, lack of response to a potentially useful antibiotic, requirement for catheter removal, and/or laparotomy. Study cases (study group) were those episodes appearing after 1996 (when the first severe cases appeared) and historic controls were episodes occurring before 1996.

RESULTS: In the study group, 18 peritonitis episodes developed in 15 patients. In the control group, 31 peritonitis episodes developed in 20 patients. There were no significant differences in clinical presentation; however, the outcome was significantly poorer for the later period. A severe outcome occurred in 50% of study versus 10% of control patients. In fact, 68% of the episodes registered before 1996 were cured in 3 days or less. Concurring with this trend, the numbers of surgical interventions and catheter removals were also higher in the study group. Strikingly, E. coli did not show changes in in vitro susceptibility testing to antibiotics, although the in vivo response was much worse.

CONCLUSIONS: We describe a change in the virulence of E. coli peritonitis episodes over the past 5 years leading to a high percentage of treatment failure, which does not depend on antibiotic sensitivity and seems to be dependent on changes in host response mechanisms.