title: Continuous ambulatory peritoneal dialysis peritonitis: broth inoculation culture versus water lysis method.
abstract: OBJECTIVE
  In the setting of empiric antibiotic treatment of peritoneal-dialysis-related peritonitis complications, the speed with which a bacteriological diagnosis can be achieved is of importance. We compare the clinical performance of two culture methods to diagnose the causative microorganisms as suggested by the International Society for Peritoneal Dialysis and the United Kingdom Health Protection Agency.
  
  
  METHODS
  We prospectively evaluated microbiological cultures of peritoneal fluid samples by the direct broth culture versus water lysis. Samples from 17 consecutive patients with dialysis-associated peritonitis were examined.
  
  
  RESULTS
  Of the 17 dialysates cultured, 14 (82.4%) were positive by one of the two methods. The final culture results agreed in 16 of 17 specimens (94.1%). The preliminary organism identification rate by Gram staining with the broth culture method was 70.6%, which was significantly greater than 17.6% by the water lysis method (p = 0.0019). In particular, the broth culture technique demonstrated superior Gram stain performance to identify Gram-positive organisms. Among the 13 dialysate samples positive by both methods, the broth culture method detected organisms faster than the water lysis method (1.3 +/- 0.7 vs. 2.6 +/- 1.6 days, p = 0.005).
  
  
  CONCLUSIONS
  Our results support the routine use of the broth culture technique using BacT/Alert blood culture bottles in order to facilitate early streamlining of empiric antibiotic therapy. Gram staining of sediments after centrifugation is associated with low diagnostic yield. Whether the lysis-centrifugation technique could provide additional value in case of peritonitis with a high likelihood of culture-negative results needs to be evaluated.
authors.affiliation: Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong, SAR, China. Chow_Kai_Ming@alumni.cuhk.net
authors.forename: Kai Ming
authors.initials: KM
authors.lastname: Chow
authors.forename: Viola Chi-Ying
authors.initials: VC
authors.lastname: Chow
authors.forename: Cheuk Chun
authors.initials: CC
authors.lastname: Szeto
authors.forename: Man Ching
authors.initials: MC
authors.lastname: Law
authors.forename: Chi Bon
authors.initials: CB
authors.lastname: Leung
authors.forename: Philip Kam-Tao
authors.initials: PK
authors.lastname: Li
mesh_terms: D000368:Aged; D001431:Bacteriological Techniques / Q000379:methods*; D018929:Cell Culture Techniques / Q000379:methods*; D015169:Colony Count, Microbial / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D010531:Peritoneal Dialysis, Continuous Ambulatory / Q000009:adverse effects*; D010538:Peritonitis / Q000175:diagnosis* / Q000382:microbiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014871:Water Microbiology