The effect of volatile fatty acids in acidified fermented piggery effluenton shiga-toxigenic and non-toxic resident strains of Escherichia coli

Aims: To examine the effects of acidified acidogenically fermented piggery effluent containing Volatile Fatty Acids (VFA) on shiga-toxigenic and resid ent strains of Escherichia coli (E. coli) as part of the development of a w aste treatment process. Methods and Results: Four shiga-toxigenic E. coli strains (O157:H7, 091.H-, 0111.H-, and 0123.H-) and four non-toxic resident enzootic strains were al l killed by 3 h treatment with fermented piggery effluent liquor (153 mmol l(-1) total VFA) at pH 4.3. The shiga-toxigenic strains showed greater sens itivity after 1 h of treatment. The fermented liquor at pH 6.8 was not inhi bitory. Conclusions: The shiga-toxigenic strains were no more resistant to the toxi c effects of VFA than the non-toxic strains tested. Significance and Impact of the Study: Shiga-toxigenic strains and resident enzootic non-toxigenic strains are equally susceptible to inactivation by t his waste treatment process and by acidified VFA in general.