Protozoan-Priming and Magnesium Conditioning Enhance Legionella pneumophila Dissemination and Monochloramine Resistance

Published on 11/06/2023 | by Waterline Admin
Cambronne ED, Ayres C, Dowdell KS, Lawler DF, Saleh NB, Kirisits MJ. Environ Sci Technol. October 2023.


  • Legionella pneumophila (Lp) gains disinfection resistance by being harboured within free-living amoebae (FLA).
  • Supplementing growth medium with 8 mM magnesium is sufficient to produce Lp grown in vitro with an infectivity equivalent to that of Lp grown via the protozoan-primed route.
  • The Lp forms tested exhibited greater monochloramine resistance than Lp grown in standard media, indicating that passage through FLA not only increases Lp’s infectivity but also enhances its monochloramine resistance.
  • Laboratory-based testing of disinfection strategies should employ conditions that simulate or replicate intracellular growth to accurately assess disinfectant resistance.


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