Comparison of Large Volume Culture to Other Methods for Isolation of Microorganisms from Dialysate

Abstract

Patients on continuous ambulatory peritoneal dialysis (CAPD) who reside long distances from a CAPD center often use community medical laboratories to document and manage episodes of peritonitis. We examined the feasibility of using large volume cultures as an alternative to more costly and labor intensive methods and to enhance earlier recovery of microorganisms from these patients. Three methods of processing dialysate from patients on CAPD were compared: (a) inoculation of 400 mL dialysate into a transfer bag (Baxter Healthcare, Inc., Round Lake, IL) containing 100 mL of 5-fold concentrate of trypticase-soy broth: (b) inoculation of 5 mL into each of two Bactec bottles (Johnston Laboratories, Towson, MD): and (c) centrifugation of 50 mL and culture of the sediment without white cell lysis on plated media and two Bactec bottles. Of the 58 specimens cultured, 34 (59%) were positive by one or more methods. Antimicrobial activity was detected in 20158 (34%) dialysates, which represent 54% of all no-growth cultures. Of the 34 culture-positive specimens, microorganisms were recovered on plated media in 22 (65%); by the centrifugation system in 32 (94%); by the routine Bactec system in 28 (82%); and by large volume culture in 30 (88%). The large volume culture system is an acceptable alternative to the more costly Bactec System and the labor intensive centrifugation method but does not significantly improve recovery of microorganisms.

Improved detection of bacterial growth in continuous ambulatory peritoneal dialysis effluent by use of BacT/Alert FAN bottles

“…is due to another cause (e.g., lipopolysaccharide [8,15,17]). Elevated leukocyte counts in the dialysates of patients just starting CAPD has been described (15).…”

“…is due to another cause (e.g., lipopolysaccharide [8,15,17]). Elevated leukocyte counts in the dialysates of patients just starting CAPD has been described (15). Differentiating inflammation due to other causes from true microbial infection is an important issue, since antimicrobial therapy may have little value in these patients and indeed may be detrimental, because it could contribute to the development of increased resistance by the normal flora of patients on CAPD.…”

“…Generally, the larger the volume of effluent cultured, the higher the detection rates. However, comparative studies indicate that the minimum volume that should be tested is 10 ml (5,13,15,21). The method chosen should include an enrichment broth with antiphagocytic and lytic properties (3,18,19).…”

“…Semiautomated blood culture systems have been used for the detection of peritonitis in CAPD effluents. Both Septi-Chek (6) and BACTEC (13,15) systems have been evaluated. Generally, methods that use these blood culture systems were equivalent or better than centrifugation methods (6,21).…”

A peritoneal dialysis patient with fatal culture‐negative peritonitis

“…5,16 These problems are, at least, partly obviated by culturing at least 10 mL of dialysate effluent 17 following dwells of at least 4 h, and sending the cultures to the laboratory for processing within 12 h. 16 Culture yields in the microbiology laboratory may also be augmented by using enrichment broth with antiphagocytic and lytic properties, 5 and semiautomated blood culture systems. 18 Subcultures of the enrichment should at least be performed on aerobic chocolate agar and anaerobic blood agar for a period of at least 7 days. One medium should also be incubated at 30 ° C to avoid missing peritonitis caused by psychrophilic microorganisms (such as Rhodotorula glutiris and certain Pseudomonas species).…”