title: [Bacterial biofilms on PVC tubing's inner surface of hemodialysis water treatment system].
abstract: OBJECTIVE
  To determine the morphology, bacteria and endotoxin content of biofilms on the inner surface of PVC tubes in hemodialysis water treatment system.
  
  
  METHODS
  We dissolved biofilms of segments before and after reverse osmosis machine for bacterial count and identification. We studied biofilm structure of segments before and after reverse osmosis machine with eyes and scanning electron microscope. Biofilms of all 7 segments were dissolved for qualitative and quantitative assay of endotoxin.
  
  
  RESULTS
  The inner surface of segment before reverse osmosis machine was homogeneously distributed with activated carbon powder deposition. The segment after reverse osmosis machine was normal. With scanning electron microscope, biofilm with successive surface and sandwich was found on the inner surface of segment before reverse osmosis machine, formed by clustering bacillus, activated carbon powder and some coccus. Bacteria of the same shape and length were found on segment after reverse osmosis machine, but fewer and looser. Bacterial culture and identification showed the former was mostly gram-negative bacillus, the latter was only a few micrococcus. Endotoxin of biofilm was between 2.0 EU/mL and 4.0 EU/mL. Quantitative assay showed: segment after softener (2.821+/-0.807) EU/mL; segment after active charcoal canister(3.635+/-0.427) EU/mL; segment before reverse osmosis machine (3.687+/-0.271) EU/mL; segment after reverse osmosis machine (2.041+/-0.295) EU/mL; exit of power pump (1.983+/-0.390)EU/mL;the 1st dead space (2.373+/-0.535) EU/mL; and the 2nd dead space (2.858+/-0.690)EU/mL.
  
  
  CONCLUSIONS
  Biofilms are found on the inner surface of segment before and after reverse osmosis machine. Endotoxin level from high to low is as follows: segment before reverse osmosis machine, segment after active charcoal canister, the 2nd dead space, segment after softener, the 1st dead space, segment after reverse osmosis machine, exit of power pump. The character of the bacteria and endotoxin of the biofilm can help us find better ways to control them.
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, China.
authors.forename: Sha
authors.initials: S
authors.lastname: Yang
authors.forename: Ke
authors.initials: K
authors.lastname: Jia
authors.forename: Youming
authors.initials: Y
authors.lastname: Peng
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Yinghong
authors.initials: Y
authors.lastname: Liu
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.forename: Fuyou
authors.initials: F
authors.lastname: Liu
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification; D018441:Biofilms / Q000254:growth & development*; D004866:Equipment Contamination / Q000517:prevention & control*; D015312:Hemodialysis Solutions / Q000032:analysis*; D006436:Hemodialysis Units, Hospital; D008070:Lipopolysaccharides / Q000032:analysis; D011143:Polyvinyl Chloride; D006435:Renal Dialysis / Q000295:instrumentation*; D014871:Water Microbiology
chemical_list: D015312:Hemodialysis Solutions; D008070:Lipopolysaccharides; D011143:Polyvinyl Chloride