Comparative Study on Changes of Bacterial Density of Three Strains of Escherichia Coli in Undernourished Water

ve To explore the regularity of changes of density of three strains of Escherichia coli in un-dernourished water at different 4 levels of temperature. Methods The simulated water samples respectively prepared with standard strains of ATCC 25922, 8099 and wild strain of Escherichia coli seperated from human faeces were in-cubated in thermostat water bath at temperatures of 5℃ , 15℃, 25℃ and 35℃ respectively. The densities of Es-cherichia coli in water samples were determined by filter membrane fluorometry quantitatively. Results No prolif-eration of Escherichia coli was found in undernourished water samples. The densities of Escherichia coli variated with the incubation durations at different temperatures according to negative exponential function:y=ae-bt. The orders of speed of decrease of Escherichia coli density in water samples were ATCC 25922 wild strain of Escherichia coli 8099 at the same temperature, and at the different temperatures: 35℃ 25℃ 15℃ . Conclusion The changes of density of different strains of Escherichia coli in the undernourished water samples closely associated with the strain ' characteristics, environment temperatures and preserving time, showed significantly differences.