Inactivating Host Bacteria for Characterization and Use of Phages

Abstract

Phage characterization for research and therapy can involve newly isolated phages propagated in pathogenic bacteria. If so, characterization requires safety-managing the bacteria. In the current study, we adapt a common and inexpensive reagent, PrimeStore (Longhorn Vaccines and Diagnostics, San Antonio, TX, USA), to safety-manage bacteria in 20 min by selectively inactivating the bacteria. No bacterial survivors are observed among >109 bacteria per ml for a representative of both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Bacillus thuringiensis). This procedure causes no detected inactivation of podophage T3, myophage T4 and siphophage 0105phi7-2. Margins of safety for PrimeStore concentration exist for bacterial inactivation and phage non-inactivation. Thus, general applicability is expected. Subsequent dialysis is used to block long-term effects on phages. Nonetheless, comparable tests should be performed for each pathogenic bacterial strain/phage. Electron microscopy of thin sections reveals inactivation-altered bacterial cytoplasm and a non-disintegrated bacterial envelope (ghosts). Ghosting of E. coli includes re-arrangement of the cytoplasm and the release of endotoxin. The activity of the released endotoxin is >99% reduced after subsequent dialysis, which also removes PrimeStore components. Ghosting of B. thuringiensis includes apparent phase separation within the cytoplasm. The primary application envisaged is biophysical and other screening of phages for therapy of infectious disease.