Survival of a Shiga toxin-encoding bacteriophage in a compost model

FEMS Microbiol Lett. 2005 Apr 15;245(2):369-75. doi: 10.1016/j.femsle.2005.03.031.

Abstract

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 (stx(2)) 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 degrees 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 degrees C is maintained for at least 5 days is effective at removing both E. coli and a model infectious Stx-encoding bacteriophage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Coliphages / genetics
  • Coliphages / physiology*
  • DNA, Viral / analysis
  • Escherichia coli / virology*
  • Polymerase Chain Reaction
  • Prophages / genetics
  • Prophages / physiology
  • Shiga Toxin 2 / genetics*
  • Soil Microbiology*
  • Soil*
  • Temperature
  • Time Factors
  • Viral Plaque Assay
  • Virus Inactivation

Substances

  • DNA, Viral
  • Shiga Toxin 2
  • Soil