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Methodology used to support changes to the Regulations for bottled water in the Food and Drugs Act of Canada, which include criteria for Pseudomonas aeruginosa (0 colony-forming units/100 mL of water), was used to assess the survival of P. aeruginosa in inoculated bottled water. The effects of P. aeruginosa on the survival of Salmonella spp. in bottled water were also investigated. The methodology used in the isolation included the use of hydrophobic grid membrane filters, a resuscitation step on tryptic soy agar, and selective plating on P. aeruginosa selective agar for P. aeruginosa and on xylose lysine desoxycholate agar for salmonellae. Pseudomonas aeruginosa and salmonellae proliferated and survived in inoculated water for up to 100 days or longer. Pseudomonas aeruginosa had a synergistic effect on the survival of salmonellae, enabling them to survive for more than 140 days in double distilled water.

A methodology used to isolate Escherichia coli O157:H7 from water and survival of this pathogen in inoculated water is described. The methodology used in the isolation of E. coli O157:H7 included the use of selective plating on Sorbitol MacConkey agar (supplemented with potassium tellurite [2.5 mg/liter], cefixime [0.05 mg/liter], and cefsulodin [10 mg/liter], and modified hemorrhagic colitis agar (also supplemented with potassium tellurite [2.5 mg/liter]) and cefsulodin [10 mg/liter]). There were no significant differences (P < 0.05) between the recoveries of E. coli O157:H7 on these two selective media. Direct plating on these selective agars was used to determine the length of time that E. coli O157:H7 was able to grow, remain viable, and be resistant to the selective agents. E. coli O157:H7 survived in inoculated water for up to > 300 days, depending on the type of water. Observation by scanning electron microscopy indicated that E. coli O157:H7 cells attached to, and multiplied on, the container walls.

The microbiological quality of bottled water sold in Canada was evaluated. A total of 114 lots of bottled water, both domestic and imported, were analyzed for aerobic colony count, coliforms, fecal coliforms, and Escherichia coli. No fecal coliforms or E. coli were found. Nineteen (46%) of the 41 lots of domestic purified water were found to exceed aerobic colony count standards and another lot exceeded coliform standards. One lot each of domestic and imported mineral water exceeded coliform standards. If mineral water were governed by the aerobic colony count standards for bottled water, then five lots each of both domestic and imported mineral water would have been found to be unsatisfactory. More surveillance of the bottled water industry in Canada is recommended.