Decreasing Enterobacter sakazakii (Cronobacter spp.) food contamination level with bacteriophages: prospects and problems.
Bottom Line: A high dose of 10(8) pfu ml(-1) of phage could effectively sterilize a broth contaminated with both high and low pathogen counts (10(6) and 10(2) cfu ml(-1)).Only when crossing this threshold, phage replication started, but it could not reduce the contamination level below 100 cfu ml(-1).Addition of trehalose or milk formula stabilized the phage preparation, which then showed excellent storage stability even at elevated temperature.
Affiliation: Nestlé Research Center, Nestec Ltd, Lausanne, Switzerland.Show MeSH
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Mentions: Next we investigated the effect of the isolated phages on E. sakazakii grown in brain–heart infusion (BHI) broth. The medium was inoculated with a high bacterial titre of 106 cfu ml−1. The culture was then split in two halves. One half received a high phage dose of 108 plaque‐forming units (pfu) ml−1[multiplicity of infection (moi) = 100] from either the isometric head Myophage F (Fig. 5A) or the prolate head T4‐like Myophage 82 (Fig. 5B), while the other halves remained uninfected. Until 3 h post inoculation the optical density reading showed a parallel OD increase in uninfected and infected cultures. This phase was followed by an OD decrease in the infected culture while the control culture demonstrated an ongoing growth (Fig. 5A and B). The 100‐fold phage titre increase, which we observed 3 h post infection, indicated that the OD decrease in the infected culture was the result of a lytic phage infection. Essentially identical results were obtained for E. sakazakii strain 316 infected with phage F (Fig. 5A) and E. sakazakii strain 368 infected with T4 like Myophage 82 (Fig. 5B). After 12 h, no outgrowth was observed for phage 82‐infected strain 368, while outgrowth was starting for phage F (data not shown).
Affiliation: Nestlé Research Center, Nestec Ltd, Lausanne, Switzerland.