Time to Positivity of Bacteria Cultures in Peritoneal Dialysis Fluid: Evaluation of Different Laboratory Techniques

Abstract

Patients with chronic kidney disease on peritoneal dialysis (PD) are susceptible to infections, with peritonitis being the primary cause of dropout. Peritoneal fluid culture is one of the essential elements for proper diagnosis and peritonitis treatment. The aim of this study was to compare the time required to obtain a positive culture using different laboratory methods. An cross-sectional study was conducted comparing different techniques for preparation and culture of bacteria in peritoneal fluid. The research was carried out with 21 sterile dialysis bags and 21 PD bags containing peritoneal fluid drained from patients without peritonitis. Fluids from the 42 PD bags were contaminated by injecting a coagulase-negative suspension and then prepared for culture using 4 distinct techniques: A - direct culture; B - post-centrifugation culture; C - direct culture after 4 h sedimentation; and D - culture after 4 h sedimentation and centrifugation. This was followed by seeding. In the 21 contaminated sterile bags, mean times to obtain a positive culture with techniques D (19.6 h ± 2.6) and C (19.1 h ± 2.3) were longer than with technique A (15.8 h ± 3.0; < 0.01), but not statistically different from group B (19.0 h ± 3.2). The same occurred in the 21 bags drained from patients, with mean times for techniques D (14.0 h ± 1.9) and C (14.5 h ± 1.7) being longer than technique A (12.22 h ± 1.94; < 0.05) but not statistically different from technique B (13.2 h ± 1.3). The sedimentation and centrifugation steps seem to be unnecessary and may delay antibiotic sensitivity test results by approximately 8 hours.

Variability in Culture-Negative Peritonitis Rates in Pediatric Peritoneal Dialysis Programs in the United States

“…We were not able to determine how many centers utilized automated blood culture systems, such as BACTEC or BacT/Alert. This technology has shown significant benefit in overall organism detection rates and decreasing time to positive culture results (16)(17)(18)(19). Only two centers (7%) reported utilizing PCR testing of the peritoneal fluid.…”

Bacteriological sampling of peritoneal dialysis fluids. How to limit negative-culture peritonitis rate?

“…Dans le cas d'une péritonite confirmée, la quantité de staphylocoques à coagulase négative contenue dans le liquide de DP diminue dès la quatrième heure, pour devenir in-détectable à 48 heures (7). Cet aspect peut être expliqué au moins en partie par la présence de leucocytes et de trace d'antibiotique dans les liquides de DP contenant des effluents de patients (8). Parmi les bacilles à Gram négatif, ce sont les Enterobacteriaceae qui prédominent largement par rapport à Pseudomonas aeruginosa (6) tique.…”

“…Les premières se sont concentrées sur l'utilisation d'un large volume de liquide de DP, afin d'augmenter les chances de détection des microorganismes. L'utilisation d'un large volume, généralement de l'ordre de 50 mL, suivi d'une sédimentation (4-6 heures), ou d'une centrifugation, afin de concentrer artificiellement les bactéries, ne permet pas un réel gain de sensibilité (8,21). Pire, l'utilisation de telles techniques pourrait différer la mise en culture du liquide de DP, et donc différer d'autant l'obtention d'un antibiogramme (8).…”