Bacteriophage inactivation to prevent carry-over in preclinical assays with mycobacteria.
5 affiliations
- 1Department of Medical Microbiology, Radboud University Medical Centre, Radboudumc Community for Infectious Diseases & Research Institute of Medical Innovation, Nijmegen, The Netherlands.
- 2TASK, Cape Town, South Africa.
- 3Department of Biological Sciences, University of Pittsburgh, Pittsburgh, United States.
- 4Department of Medical Microbiology, Radboud University Medical Centre, Radboudumc Community for Infectious Diseases & Research Institute of Medical Innovation, Nijmegen, The Netherlands. [email protected].
- 5TASK, Cape Town, South Africa. [email protected].
Abstract
Background
Bacteriophage carry-over, the continued lytic activity of residual phages after experimental sampling, poses a significant challenge in bacteriophage research, potentially skewing experimental results, particularly in the context of preclinical studies where perceived laboratory success may not translate clinically. These inaccuracies, relevant across various bacterial species, underscore the necessity for robust mitigation strategies. This study provides an overview of strategies to mitigate phage carry-over, evaluating their performance on a combination of three mycobacteriophages with lytic activity against M. tuberculosis.Results
We investigated three inactivation methods, including ferrous ammonium sulfate (FAS) and citrate for in vitro applications and N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) for sputum decontamination. The citrate buffer offered limited and specific phage inactivation, but FAS was effective in inactivating all three mycobacteriophages (FionnbharthΔ45Δ47, Muddy HRMN0157-2, and Fred313cpm-1Δ33). With pH adapted to 5.0, FAS did not significantly reduce M. tuberculosis H37Rv viability after five minutes exposure. Phage carry-over was determined to be phage-dependent; FionnbharthΔ45Δ47 exhibited the most significant reduction in M. smegmatis colony forming units without phage inactivation measures. Furthermore, we showed that NALC-NaOH methods, commonly used for sputum decontamination, are highly effective in reducing phage titers in aqueous solutions and human sputum samples.Conclusions
This study demonstrates the heterogenous and phage-dependent efficacy of available inactivation buffers, underscoring the critical necessity for researchers to empirically screen their specific phage isolates against chosen inactivation methods. This is crucial to ensure that observed antibacterial effects are correctly attributed to phage activity during the experimental period, rather than to uncontrolled phage carry-over, thereby enhancing the reliability and interpretability of results.
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BibTeX
@article{torres2026bacteriophage,
title = {{Bacteriophage inactivation to prevent carry-over in preclinical assays with mycobacteria.}},
author = {M Pozuelo Torres and C Morrow and C A Guerrero-Bustamante and G F Hatfull and A H Diacon and J van Ingen and S Janssen},
journal = {BMC microbiology},
year = {2026},
month = aug,
doi = {10.1186/s12866-026-05431-8},
url = {https://europepmc.org/article/MED/42958013},
note = {CC BY},
}
RIS
TY - JOUR
TI - Bacteriophage inactivation to prevent carry-over in preclinical assays with mycobacteria.
AU - M Pozuelo Torres
AU - C Morrow
AU - C A Guerrero-Bustamante
AU - G F Hatfull
AU - A H Diacon
AU - J van Ingen
AU - S Janssen
PY - 2026
DA - 2026/08/04
JO - BMC microbiology
DO - 10.1186/s12866-026-05431-8
UR - https://europepmc.org/article/MED/42958013
AB - Background Bacteriophage carry-over, the continued lytic activity of residual phages after experimental sampling, poses a significant challenge in bacteriophage research, potentially skewing experimental results, particularly in the context of preclinical studies where perceived laboratory success may not translate clinically. These inaccuracies, relevant across various bacterial species, underscore the necessity for robust mitigation strategies. This study provides an overview of strategies to mitigate phage carry-over, evaluating their performance on a combination of three mycobacteriophages with lytic activity against M. tuberculosis.Results We investigated three inactivation methods, including ferrous ammonium sulfate (FAS) and citrate for in vitro applications and N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) for sputum decontamination. The citrate buffer offered limited and specific phage inactivation, but FAS was effective in inactivating all three mycobacteriophages (FionnbharthΔ45Δ47, Muddy HRMN0157-2, and Fred313cpm-1Δ33). With pH adapted to 5.0, FAS did not significantly reduce M. tuberculosis H37Rv viability after five minutes exposure. Phage carry-over was determined to be phage-dependent; FionnbharthΔ45Δ47 exhibited the most significant reduction in M. smegmatis colony forming units without phage inactivation measures. Furthermore, we showed that NALC-NaOH methods, commonly used for sputum decontamination, are highly effective in reducing phage titers in aqueous solutions and human sputum samples.Conclusions This study demonstrates the heterogenous and phage-dependent efficacy of available inactivation buffers, underscoring the critical necessity for researchers to empirically screen their specific phage isolates against chosen inactivation methods. This is crucial to ensure that observed antibacterial effects are correctly attributed to phage activity during the experimental period, rather than to uncontrolled phage carry-over, thereby enhancing the reliability and interpretability of results.
SN - 1471-2180
ER -