Comparison of methods for processing dialysate in suspected continuous ambulatory peritoneal dialysis-associated peritonitis.

Three methods of processing dialysate from patients on continuous ambulatory peritoneal dialysis and with suspected peritonitis were compared: (a) direct inoculation of 10 ml of dialysate into an Isolator tube, (b) direct inoculation of 5 ml of dialysate into each of two Bactec blood culture bottles (NR 6A and 7A), and (c) centrifugation of 50 ml upon receipt in the laboratory and culture of the sediment. A diagnosis of peritonitis was made in 33 of 52 suspected episodes. Pathogens were recovered by Isolator in 26 of the 33 specimens, by Bactec in 21, by centrifugation in 25, and by any method in 27. Time to detection of positivity was the same for Isolator and Bactec in 20 of 21 cases and for Isolator and centrifugation in 21 of 24 cases. Identification was available 24-48 hr earlier with Isolator than with centrifugation in three of 24 cases and 24 hr earlier with Isolator than Bactec in 20 of 21 cases.