Abstract: TH-PO0452
Fast-Tracking Dialysis Water Quality: Flow Cytometry as a Superior Microbial Monitoring Tool
Session Information
- Hemodialysis: Novel Markers and Case Reports
November 06, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Dialysis
- 801 Dialysis: Hemodialysis and Frequent Dialysis
Authors
- Lucena, Rui, Fresenius Medical Care Deutschland GmbH, Bad Homburg, HE, Germany
- Feurle, Juliane K, Fresenius Medical Care Deutschland GmbH, Bad Homburg, HE, Germany
- Gil, Célia, Unidade Local de Saude de Lisboa Ocidental, Lisbon, Lisbon, Portugal
- Ferreira, Aníbal, Universidade Nova de Lisboa Medical School, Lisbon, Lisbon, Portugal
- Ponce, Pedro, Nephrocare Portugal SA, Lisbon, Lisbon, Portugal
- Canaud, Bernard J., Universite de Montpellier, Montpellier, Occitanie, France
Background
Ensuring microbial quality of dialysis water is essential for patient safety, especially in high-volume online hemodiafiltration. Standard monitoring uses heterotrophic plate counts (HPC), which require 7 days of incubation. This delay hampers timely interventions. Flow cytometry (FCM) has emerged as a promising alternative, enabling rapid and sensitive quantification of microbial cells. Key differences are shown in Figure 1.
Methods
In a 36-week prospective study, weekly water samples were collected under real-world conditions from the loop return of a dialysis clinic. Each sample was tested using both HPC (ISO 23500-3; pour-plate on R2A agar, incubated 7 days at 17–23°C) and FCM (AQU@Sense MB cytometer, DNA staining with PI and SYBR Green I). Results were compared in terms of sensitivity, time-to-result, and ability to detect early deviations from microbial quality standards.
Results
Microbial load measurement obtained via FCM where significantly higher than those from HPC, even in samples that were compliant with HPC-based quality standards. This indicates that FCM offers greater sensitivity and detect microbial contamination that may go unnoticed with conventional culture-based methods.
Conclusion
Flow cytometry provides a rapid, sensitive alternative to culture-based microbial monitoring of dialysis water. Its near real-time performance enables earlier intervention and may improve patient safety. Adoption of FCM in routine protocols could modernize quality control practices. Further studies are needed to define regulatory thresholds and evaluate cost-effectiveness.
FCM vs HPC (Mann-Whitney test)
| Sampling point | Mann-Whitney test | FCM (ICC/mL) (n=36) | HPC (CFU/mL) (n=36) | p-value |
| Dialysis water distribution system (loop return) | Mean (SD) | 43.33 (21.65) | 11.81 (12.05) | <0.001 |
| Median (Min.-Max.) | 40.00 (10 - 100) | 7.50 (0 - 50) |
Figure 1. Key Characteristics of HPC vs. FCM.
Figure 2. FCM vs HPC outcomes.