Improving peritoneal dialysis fluid culture-positivity yield from 2022 to 2023

Background: Microbiological testing of peritoneal dialysis bags for peritonitis often yields culture-negative results. Culture-negative samples should not exceed 15% according to the International Society for Peritoneal Dialysis. To reduce this issue, the addition of a blood culture bottle incubation step to the culture process was introduced at the Infection Control Services Laboratory (ICSL) of the National Health Laboratory Services (NHLS). Objectives: The aim of the study was to ascertain if the change in methodology increased the culture-positivity yield and reduced the culture-negative percentage. Method: Data from the NHLS Central Data Warehouse (CDW) were analysed to compare the culture-positive results over two periods: June–December 2022 when the non-blood culture (B/C) bottle method was used and January–July 2023 when the B/C bottle method was implemented. Results: The non-B/C culture method yielded a 23% culture-positivity yield, whereas the B/C bottle-based method yielded a 51% culture-positivity yield. However, the culture-negative yield for the B/C bottle-based method was high at 49%. Conclusion: The change in dialysis bag processing in 2023 led to a more than doubling in culture-positivity yield. However, the culture-negative percentage remained high. As a result, further modifications to the methodology are needed. Contribution: The study findings illustrate that the addition of the B/C bottle incubation step significantly improved peritoneal dialysis bag culture yields which directly impacts patient management.