Inflammation boosts bacteriophage transfer between Salmonella spp.

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Science  17 Mar 2017:
Vol. 355, Issue 6330, pp. 1211-1215
DOI: 10.1126/science.aaf8451

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The parasite of my parasite is my friend?

Virulence factors of pathogenic bacteria can be swapped by means of bacterial viruses called phages. In turn, the pathogenic bacteria are under attack by the hosts' immune responses. Diard et al. discovered that SopEϕ, a phage parasite of pathogenic Salmonella species, is encouraged to spread between bacteria by the mouse host's inflammatory responses. Conversely, mucosal vaccination against Salmonella reduced inflammatory responses and curbed the transfer of SopEϕ to naïve bacteria.

Science, this issue p. 1211


Bacteriophage transfer (lysogenic conversion) promotes bacterial virulence evolution. There is limited understanding of the factors that determine lysogenic conversion dynamics within infected hosts. A murine Salmonella Typhimurium (S.Tm) diarrhea model was used to study the transfer of SopEΦ, a prophage from S.Tm SL1344, to S.Tm ATCC14028S. Gut inflammation and enteric disease triggered >55% lysogenic conversion of ATCC14028S within 3 days. Without inflammation, SopEΦ transfer was reduced by up to 105-fold. This was because inflammation (e.g., reactive oxygen species, reactive nitrogen species, hypochlorite) triggers the bacterial SOS response, boosts expression of the phage antirepressor Tum, and thereby promotes free phage production and subsequent transfer. Mucosal vaccination prevented a dense intestinal S.Tm population from inducing inflammation and consequently abolished SopEΦ transfer. Vaccination may be a general strategy for blocking pathogen evolution that requires disease-driven transfer of temperate bacteriophages.

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