Pass T, Wright R, Sharp B, Harding G B
Water Testing Laboratory, Morehead State University, Ky 40351, USA.
Blood Purif. 1996;14(2):136-45. doi: 10.1159/000170255.
Recommended culture methods for monitoring bacterial contamination of H2O, dialysate and bicarbonate concentrate in dialysis centers in the USA involves culturing these fluids for 48 h at 37 degrees C. A variety of media and commercial culture methods are accepted for monitoring these fluids. Over a 3-month a comparison was made between an acceptable culture method, tryptic soy agar (TSA) employing the pour plate (PP) technique at 37 degrees C for 48 h, and PP cultures on standard methods agar (SMA) and R2A agar, incubated at ambient temperature (23 degrees C) for 48, 72, 168 h. Increases in the colony counts over time occurred for all three fluids. However, counts wee greater on SMA and R2A than on TSA. The increases over the standard 48-hour TSA cultures ranged as high as 10(4) times for 23 degrees C cultures at 7 days of incubation. Endotoxin levels even in the most contaminated samples were found to be below the acceptable 5 EU/ml recommended for reprocessor water. Bacterial colonies that appeared at 48, 72 and 168 h were isolated and identified. Pseudomonas, Moraxella, Acinetobacter and CDC group VI C-2 were among some of the common bacteria isolated. This study indicates that the media utilized, the time and temperature of incubation may result in a significant underestimation of the bacterial population of water and dialysis fluids, thus potentially placing the patient at a higher risk.
美国透析中心监测水、透析液和碳酸氢盐浓缩液细菌污染的推荐培养方法是将这些液体在37摄氏度下培养48小时。多种培养基和商业培养方法可用于监测这些液体。在3个月的时间里，对一种可接受的培养方法进行了比较，即采用倾注平板（PP）技术在37摄氏度下培养48小时的胰蛋白胨大豆琼脂（TSA），以及在标准方法琼脂（SMA）和R2A琼脂上进行的PP培养，在环境温度（23摄氏度）下培养48、72、168小时。所有三种液体的菌落计数均随时间增加。然而，SMA和R2A上的计数高于TSA。在23摄氏度培养7天的情况下，与标准的48小时TSA培养相比，增加幅度高达10（4）倍。即使在污染最严重的样本中，内毒素水平也低于再处理用水推荐的可接受的5 EU/ml。对在48、72和168小时出现的细菌菌落进行了分离和鉴定。分离出的常见细菌包括假单胞菌、莫拉菌、不动杆菌和疾病控制与预防中心（CDC）VI C-2组。这项研究表明，所使用的培养基、培养时间和温度可能会导致对水和透析液中细菌数量的显著低估，从而可能使患者面临更高的风险。
