Bacteriophages that carry the Shiga toxin gene (stx) represent an additional hazard in cattle manure-based fertilizers in that their survival could lead to toxigenic conversion of Escherichia coli and other bacteria post-composting. A Stx-phage in which the Shiga toxin (stx2) gene was inactivated by insertion of a chloramphenicol resistance gene was used in combination with a rifampicin-resistant E. coli host where RecA is constitutively activated so that all infectious phage particles could be enumerated by plaque assay. PCR-based confirmation methods and the additional application of a host enrichment protocol ensured that very low numbers of surviving bacteriophage could be detected and unequivocally identified. Stx-bacteriophage numbers declined rapidly over the first 48 h and none could be detected after 3 days. The host enrichment method was applied after 6 days and no bacteriophages were recovered. While addition of fresh E. coli cells at intervals after the compost temperature had reduced below 40°C demonstrated that E. coli growth could be supported in the compost, Stx-phages or their lysogens were never detected. Here, we demonstrate that composting animal manure for 40 days during which a temperature of >60°C is maintained for at least 5 days is effective at removing both E. coli and a model infectious Stx-encoding bacteriophage. © 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
Johannessen, G. S., James, C. E., Allison, H. E., Smith, D. L., Saunders, J. R., & McCarthy, A. J. (2005). Survival of a Shiga toxin-encoding bacteriophage in a compost model. FEMS Microbiology Letters, 245(2), 369–375. https://doi.org/10.1016/j.femsle.2005.03.031