| Summary: | 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 >10<sup>9</sup> bacteria per ml for a representative of both Gram-negative bacteria (<i>Escherichia coli</i>) and Gram-positive bacteria (<i>Bacillus thuringiensis</i>). 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 <i>E. coli</i> 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 <i>B. thuringiensis</i> includes apparent phase separation within <i>the</i> cytoplasm. The primary application envisaged is biophysical and other screening of phages for therapy of infectious disease.
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