title: Heat and lime-treatment as effective control methods for E. coli O157:H7 in organic wastes.
abstract: Land-application of abattoir wastes is economically appealing and may provide an effective means of closing the nutrient cycling loop. This practise is constrained, however, by legislation which necessitates pre-treatment to remove pathogenic micro-organisms prior to land-spreading. Here we investigated whether heat-treatment or lime addition could eliminate Escherichia coli O157:H7 from three contrasting abattoir wastes. We found that treatment at 60 degrees C for 10 min effectively eradicated the organism while treatment for the same length of time at 50 degrees C led to 2-4 log reductions, but not a complete kill. Temperatures of 72 degrees C induced waste solidification rendering its use impractical. The potential for re-growth in heat-treated and untreated wastes was also investigated. Survival was significantly greater in heat-treated wastes, although the difference was less than half a log unit in magnitude. This effect of heat-treatment on pathogen survival appeared to be ameliorated when wastes were mixed with soil. No viable E. coli O157:H7 cells were recovered from any waste after application of lime (CaO) at a rate of 10 gl(-1), even after enrichment. Our results indicate that pasteurisation-style or liming treatments may provide a suitable alternative method for reducing pathogen loads in abattoir wastes, so that they can be applied to land with minimal biological risk.
authors.affiliation: School of the Environment and Natural Resources, College of Natural Sciences, Bangor University, Gwynedd, UK.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Avery
authors.forename: A Prysor
authors.initials: AP
authors.lastname: Williams
authors.forename: Ken
authors.initials: K
authors.lastname: Killham
authors.forename: David L
authors.initials: DL
authors.lastname: Jones
mesh_terms: D000003:Abattoirs; D017610:Calcium Compounds / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D019453:Escherichia coli O157 / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007220:Industrial Waste / Q000517:prevention & control*; D010087:Oxides / Q000494:pharmacology*; D012722:Sewage / Q000382:microbiology*; D013242:Sterilization / Q000379:methods*; D018505:Waste Management / Q000379:methods*
chemical_list: D017610:Calcium Compounds; D007220:Industrial Waste; D010087:Oxides; D012722:Sewage; C016538:lime