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OVERVIEW: DISINFECTION OF HELICOBACTER PYLORI AND AEROMONAS SPECIES
Citation:
Boczek*, L A., C H. Johnson*, D J. Reasoner*, E. Rice, AND S. Sabaratnam. OVERVIEW: DISINFECTION OF HELICOBACTER PYLORI AND AEROMONAS SPECIES. Presented at U.S. EPA's Research on Microoganisms in Drinking Water Workshop, AWBERC, Cincinnati, 8/5-7/2003.
Description:
Helicobacter pylori and Aeromonas hydrophila are contaminants listed on the USEPA's 1998 Contaminant Candidate List (CCL).The sensitivity of H. pylori to chlorine and of Aeromonas spp. to inactivation by free chlorine, chloramine and ultraviolet (UV) was examined. Selective and non-selective monitoring media were evaluated to assess recovery of chlorine or UV-stressed Aeromonas spp. Results of experiments using free chlorine showed that the H. pylori and Aeromonas spp. were readily inactivated under all conditions studied. H. pylori showed more than 3.5 orders of magnitude inactivation by 0.5 mg /L chlorine in 80 seconds at 5 C. The Aeromonas spp. were inactivated by more than 5 orders of magnitude within a one minute exposure to free chlorine at pH 7 or 8, and at 5 C or 25 C. Reductions of the Aeromonas spp with 2.0 mg/L of monochloramine reached approximately 2 orders of magnitude at pH 8.0 for 4 minutes and greater than five orders of magnitude inactivation after 8 minutes of exposure. Aeromonas spp. were found to be sensitive to UV irradiation, with fluences of less than 7 mj/cm2 giving between 5-7 log10 reductions. For free chlorine there was no observable difference in recovery of chlorine-stressed Aeromonas spp organisms between selective and non-selective media. However, with UV disinfection, some Aeromonas spp. counts on non-selective media were significantly higher than those obtained on selective agar. These findings suggest that selective agars may underestimate the number of viable Aeromonas recovered after exposure to UV irradiation.