Abstract
Listeria monocytogenes serotype 4b strains are the most prevalent clinical isolates and are widely found in food processing environments. Bacteriophages are natural viral predators of bacteria and are a promising biocontrol agent for L. monocytogenes. The aims of this study were to characterize phages that specifically infect serotype 4b strains and to assess their ability to inhibit the growth of serotype 4b strains. Out of 120 wild Listeria phages, nine phages were selected based on their strong lytic activity against the model serotype 4b strain F2365. These nine phages can be divided into two groups based on their morphological characteristics and host range. Comparison to previously characterized phage genomes revealed one of these groups qualifies to be defined as a novel species. Phages LP-020, LP-027, and LP-094 were selected as representatives of these two groups of phages for further characterization through one-step growth curve and inhibition of serotype 4b L. monocytogenes experiments. Listeria phages that target serotype 4b showed an inhibitory effect on the growth of F2365 and other serotype 4 strains and may be useful for biocontrol of L.monocytogenes in food processing environments.
Highlights
Listeria monocytogenes is a Gram-positive foodborne pathogen that infects humans and animals [1]
Presence or absence of these sugars corresponds to the various serotypes of L. monocytogenes [16]; Listeria phages show some level of serotype specificity [17]
Phages were stained with 1% phosphotungstic acid and imaged at a final magnification of ×69,700–83,600
Summary
Listeria monocytogenes is a Gram-positive foodborne pathogen that infects humans and animals [1]. Within the United States alone, there is an estimated 2518 annual cases, with a 20% mortality rate [8,9], and economic losses caused by listeriosis were more than $3.1 billion in 2018 [10]. Self-replication capability, and tolerance of a wide range of temperatures and pHs [12] make bacteriophages a promising candidate for biocontrol of L. monocytogenes in the food processing environment [13]. Listeria phage biocontrol products have been approved for use by the United States Food and Drug Administration since 2006. These products are marketed to control L. monocytogenes contamination on food and in food processing plants. Presence or absence of these sugars corresponds to the various serotypes of L. monocytogenes [16]; Listeria phages show some level of serotype specificity [17]
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