Abstract:

Objective To compare detection ratio of bacterial colony count in dialysis water with different media and different incubation conditions, and to search for suitable method to detect  bacteria from dialysis water. Methods Between January and December of 2012, 152 samples of hemodialysis water from Hemodialysis Center of Renji Hospital were randomly collected. The samples were cultured in duplicate on spread plates with blood agar, tryptic soy agar (TSA), Reasoner′s 2A (R2A), and tryptone glucose extract agar (TGEA), respectively, at 20, 30, and 35 ℃ for 48-168 h.  After incubation, the numbers of colonies were quantified. Results In blood agar, the bacterial colony counts of dialysis water were the lowest with significant differences compared to TGEA and R2A culture media (P<0.05, P<0.01). In R2A agar, the detection rate of bacteria at 20 ℃ for 168 h was significantly higher than that in blood agar at 35 ℃ for 48 h (67.1% vs 43.4%, P<0.01). Bland-Altman analysis showed that there was close consistence between the detection rates of bacteria in R2A agar at 20 ℃ for 168 h and in TGEA agar at 30 ℃ for 120 h. Conclusion The method of R2A or TGEA agar culture could improve the detection rate of bacterial colony count in dialysis water in comparing to the method of blood culture. The method of R2A at 20 ℃ for 168 h or TGEA at 30 ℃ for 120 h is the suitable method for bacteria detection in dialysis water.

Key words: bacterial culture, hemodialysis, culture medium, dialysis water