Changing microbiology and outcomes of PD-associated peritonitis over four decades.

Background: Peritoneal dialysis (PD)-associated peritonitis remains a major complication affecting patient outcomes and modality survival. This study aims to evaluate temporal trends in pathogen distribution and antibiotic susceptibility over four decades as well as clinical outcomes in PD-associated peritonitis. Methods: We retrospectively analyzed 832 peritonitis cultures of PD patients across four decades from 1979 to 2024 treated at Robert Bosch Hospital, Stuttgart (Germany). For longitudinal comparison of pathogen distribution and antibiotic susceptibility, the study period was divided into four time periods: P1 (1979-1992), P2 (1993-2003), P3 (2004-2014), and P4 (2015-2024). Clinical response and outcomes were assessed in P4. Results: Gram-positive bacteria was the most frequent causative organisms (56%), followed by Gram-negative bacteria (30%) and culture-negative peritonitis (CNP, 13%). Gram-negative peritonitis increased significantly in P4 compared to P1-P3, while coagulase-negative staphylococci (CNS) declined from 31% in P1 to 14% in P4 (P = .0446). Vancomycin susceptibility among Gram-positive organisms remained high, whereas cefazolin susceptibility changed over time. In P4, the overall cure rate was 63%, with the highest in gram-positive (72%) and lowest in polymicrobial peritonitis (43%).Regarding clinical outcomes, transition to permanent hemodialysis (HD) was significantly more frequent in Gram-negative than Gram-positive peritonitis (27% vs. 12%; P = .03). Both catheter removal and transition to permanent HD occurred significantly more often in polymicrobial peritonitis (54% and 40%) compared with Gram-positive (24% and 12%; P = .001 and P = .0008) and CNP (30% and 17%; P = .01 and P = .04). Regarding individual pathogens, Staphylococcus aureus (MSSA) was associated with a significantly higher catheter removal rate compared to other Gram-positive organisms. Conclusion: Our findings show temporal changes of microbiological spectrum of PD-associated peritonitis over four decades. Polymicrobial and Gram-negative peritonitis were associated with poorer outcomes, emphasizing the need for ongoing microbiological surveillance and antibiotic stewardship to optimize PD care.