Investigation of the Survial of Escherichia Coli O157∶H7 in Eight Kinds of Water Quality

Objective To investigate the survival of EHEC O157:H7 in various kinds of water quality.Methods We collected eight kinds of water sapmples and added the solution of the fifth generation of EHEC O157:H7 933 strain bacteria suspended with appropriate concentration to the water samples which had been sorted in the laboratory and made the concentration of bacteria infected up to 10⁶ CFU/ml,then preserved these water samples under the condition of 4℃ and 25℃ individually.Samples were collected once every five days after infecting bacteria,then the bacteria were separated and identified.The bacteria were sifted primarily through SMAC、disaccharidferric、lysine dynamic agar before separation and identification.The Colonys whose feature coincided with EHEC O157∶H7 were counted after the assurance of bacteria biochemical identification and serum identification.Results The survial time of EHEC O157:H7 lasted 15 days at least and 40 days at most after they polluted water samples;the Survival number of EHEC O157:H7 indicated acute attenuation curve in swimming-pool new water or mineral water under 4℃ and the survival number slightly indicated the plateau near 10⁴CFU/ml after it decreased by 2 orders of magnitude acutely in 15 days in well-water under 4℃ and the survival number's change of EHEC O157:H7 indicated double-plateau attenuation curve in other samples under 4℃;The survival numberof EHEC O157:H7 in well-water under 25℃ indicated plateau's another acute attenuation after it decreased by 3 orders of magnitude acutely in 5 days;The survival numbers all indicated acute attenuation curves under 25℃ in other water samples;The survival numbers of EHEC O157:H7 under 25℃ in other water samples were all fewer than in the same time's samples under 4℃ except that their survival numbers were higher in swimming-pool old water on the tenth day than in that under 4℃;The survival numbers of EHEC O157:H7 all indicated the phenomenon of attenuation's sudden acceleration when they decreased to 10⁴CFU/ml in various kinds of water samples under different temperatures except in well2water under 25℃.Conclusion The survival of EHEC O157:H7 in water quality is associated tightly with the kinds of water quality、surrounding's temperature、organic substance in water and content of bacteriostatic substance;Attention should been paid to the survival difference of this kind of bacterium when searching source of infection and dealing with infectious water,then different measurements are adopted; No drinking fresh water is advocated in daily preventive work and supervision and monitoring should been strengthened in the production of pure water and mineral water;Water in swimming-pool should be changed and swimming-pool be sterilized on the stipulation.