Open AccessSurvival of a Shiga toxin‐encoding bacteriophage in a compost model
Author(s) -
Johannessen Gro S.,
James Chloe E.,
Allison Heather E.,
Smith Darren L.,
Saunders Jon R.,
McCarthy Alan J.
Publication year - 2005
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2005.03.031
Subject(s) - shiga toxin , microbiology and biotechnology , bacteriophage , escherichia coli , biology , phage typing , lysogen , toxin , compost , bacteria , shiga like toxin , virology , gene , serotype , genetics , ecology
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 °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.