Survival and recovery of Escherichia coli O157:H7 in inoculated bottled 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.