Title: Effect of Chlorine Dioxide Treatment on Methylobacterium in Dental Waterlines
Lauritz Jensen (Presenter)
Denise Olivas, Midwestern University
Aseel Murad, Midwestern University
John Mitchell, Midwestern University
Objectives: In a surveillance study of dental clinic waterlines, Methylobacterium aquaticum, an exquisite biofilm producer, was routinely recovered from water samples. This bacterium is considered to be only an environmental contaminant and has never been isolated from humans; however, other species of the genus have been implicated in health care-associated infections—most notably in immunocompromised patients. Detecting Methylobacterium in waterlines is difficult, especially when employing routine microbiologic lab testing procedures. In the past, most of the Methylobacterium colony forming units (CFU) were missed altogether because of its preference for ambient temperatures, and because the colonies were overgrown by normal human and environmental flora at 37°C. Culturing on R2A agar at room temperature for a 5-day period allows for formation of discrete CFU. This project assessed the ability of a standard waterline-treatment, MicroClear (Rowpar Pharmaceuticals, Scottsdale, AZ) to eradicate Methylobacterium.
Methods: Samples of water from dental units with suspected Methylobacterium levels were collected and plated on R2A Agar at 25C. Waterlines were then disinfected (shocked) with 10% MicroClear (chlorine dioxide) for 48 hours, rinsed with reverse osmosis (RO) water, refilled, and samples again collected for culture plating. To compare the effectiveness of the water disinfection-treatment, a t-test (paired two sample for means) was employed with α=0.05.
Results: The CFU counts for the Methylobacterium before and after treatment were not statistically different. The p value was determined to be 0.1530.
Conclusions: In a companion set of experiments, in vitro studies showed that raising the RO water temperature to 45 °C for 4 days completely eliminated all Methylobacterium growth. We are investigating the possible synergistic effect of temperature and MicroClear treatments.