Biofilms in Hemodialysis

In December 2002, all U.S. chronic hemodialysis centers were surveyed regarding selected patient care practices and dialysis-associated diseases. The results were compared with similar surveys conducted in previous years. In 2002, 85% of hemodialysis centers were free-standing and 81% operated for profit; the proportion of centers operating for profit has increased each year since 1985. During 1995-2002, the percentage of patients who received dialysis through central catheters increased from 13% to 26%; this trend is worrisome, as infections and antimicrobial use are higher among patients receiving dialysis through catheters. However, during the same period, the percentage of patients receiving dialysis through fistulas increased from 22% to 33%. The percentage of centers reporting one or more patients infected or colonized with vancomycin-resistant enterococci (VRE) increased from 12% in 1995 to 30% in 2002. During 1997-2002, the percentage of patients vaccinated against hepatitis B virus (HBV) infection increased from 47% to 56% and the percentage of staff vaccinated increased from 87% to 90%. In 2002, routine testing for antibody to hepatitis C virus (anti-HCV) was performed on patients at 64% of centers; anti-HCV was found in 7.8% of patients. In 2001, the Centers for Disease Control (CDC) published Recommendations for Preventing Transmission of Infections among Chronic Hemodialysis Patients. Centers were surveyed regarding their awareness of the recommendations and about a variety of infection control practices. In general, the incidence of HBV and HCV was not substantially different for the infection control practices evaluated, including where staff obtain clean supplies for patient treatment, reuse of unused and unopened supplies, and practices for changing external transducer filters/protectors. However, in 2002, the incidence of HBV infection was higher among patients in centers where injectable medications were prepared on a medication cart or medication area located in the treatment area compared to a dedicated medication room. Also, those centers that used a disposable container versus a nondisposable container for priming the dialyzer had a significantly lower incidence of HCV.

In the present study, we examined the effect of ozonated water on oral microorganisms and dental plaque. Almost no microorganisms were detected after being treated with ozonated water (4 mg/l) for 10 s. To estimate the ozonated water-treated Streptococcus mutans, bacterial cells were stained with LIVE/DEAD BacLight Bacterial Viability Kit. Fluorescence microscopic analysis revealed that S. mutans cells were killed instantaneously in ozonated water. Some breakage of ozonated water-treated S. mutans was found by electron microscopy. When the experimental dental plaque was exposed to ozonated water, the number of viable S. mutans remarkably decreased. Ozonated water strongly inhibited the accumulation of experimental dental plaque in vitro. After the dental plaque samples from human subjects were exposed to ozonated water in vitro, almost no viable bacterial cells were detected. These results suggest that ozonated water should be useful in reducing the infections caused by oral microorganisms in dental plaque.

The effectiveness of cleaning was investigated through food factory trials and laboratory experiments using a naturally occurring biofilm from a food factory environment and generated biofilms. The efficacy of factory cleaning and disinfection programmes was assessed by swabbing and total viable count (TVC) analysis of surfaces before cleaning, after cleaning and after disinfection. Cleaning produced a 0.91 log reduction in the attached population. Investigation of the effectiveness of a variety of cleaning methods in the removal of a naturally occurring food factory biofilm showed that the high pressure spray and the mechanical floor scrubber, which use a high degree of mechanical action, were most effective. Cleaning trials with biofilms of Pseudomonas aeruginosa or Staphylococcus aureus showed that spraying with water at pressures of 34.5, 51.7 and 68.9 bar did not significantly increase the removal, as assessed by direct epifluorescent microscopy (DEM) and swabbing and TVC analysis, beyond the three log reduction observed at 17.2 bar. The effect of spray time at 17.2 bar showed that increasing spray time from 1 to 10 s did not significantly increase removal of Ps. aeruginosa biofilm. Investigation of the optimum distance of the spray lance from the surface at 17.2 bar was found to be between 125 and 250 mm. The use of an alkaline, acidic or neutral detergent prior to spraying with water at 17.2 bar did not significantly increase the removal of Ps. aeruginosa or Staph. aureus. However, the acidic and alkaline products significantly (P = 0.05) affected the viability of Staph. aureus and Ps. aeruginosa, respectively, thereby minimizing the potential for the spread of contamination.