| Abstract: |
treated by maintenance hemodialysis has increased sharply during the past 30 years. In the United States 1999, more than 3,000 hemodialysis centers had >190,000 chronic hemodialysis patients and >60,000 staff members (National Institutes of Health. 1999 ). Chronic hemodialysis patients are at high risk for infection because the process of hemodialysis requires vascular access for prolonged periods.Patients with chronic renal insufficiency suffer from abnormalities of the immune system, as a direct result of uremia and its metabolic consequences, making them more susceptible to infections. Such abnormalities include impairment of the action of neutrophils, lymphocytes B and T and monocytes, leading to defective antigen processing, antibody production and cell-mediated immune response and thus to an increased incidence of microbial infections (Pontoriero et al. ,2003 ; Jaber ,2005) .Each patient using a kidney machine is exposed to between 18,000 and 36,000 L of water a year, from which, if it were not properly treated, a variety of chemical, bacterial and toxic contaminants could be transferred to the patients.The source of water used in hemodialysis consists basically of drinking water, purified by various techniques, whose composition and quality depend on its origin (Silva et al.,1996).In Zagazig university hospitals hemodialysis units, a frequently used system of water treatment is reverse osmosis.Typically, water from the public supply passes through mechanical filters, water softeners, charcoal filters, deionizers and the reverse osmosis filter and is finally stored in tanks for subsequent distribution through polyvinyl chloride (PVC) tubing to the whole water system of the unit . In such a system, the tubes, tanks and taps represent potential reservoirs for microorganisms that contribute to biofilms which, once formed, are extremely hard to eradicate by chemical or mechanical means ( Oie et al. ,2003; Capelli et al. ,2006).Some studies reported the presence of biofilm in the tubing carrying hemodialysis fluids and noted its high resistance to biocides.
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