The effects of the virulence plasmid ColV, I-K94 on the survival of Escherichia coli in sewage effluent.

Escherichia coli 1829 and its mucoid and non-mucoid ColV, I-K94+ derivatives (1829 ColVMuc and 1829 ColVNM) were tested for survival in final sewage effluent (FE) at 20 degrees C. All three strains survived well for 24 h; in some experiments there was also good survival at 48 h but in others there was marked loss of viability. There were only small differences between the strains in their ability to survive in FE i.e. neither ColV, I-K94 nor the mucoid character consistently increased or reduced survival markedly. To assess which factors in FE influence survival, the three strains were also tested in heated FE, filtered FE and chloroform-treated FE. All three strains survived well in heated FE at 20 degrees C but 1829 ColVNM, lost viability much more markedly than the other two strains in filtered FE or chloroform-treated FE. In spite of the poor nutrient level in FE, there was a marked increase, in bacteriophage number in those cultures incubated in chloroform treated FE.