Host range and in vitro lysis of Listeria monocytogenes seafood isolates by bacteriophages

Abstract

Listeria-infecting bacteriophages (listeriaphages) can be used to control Listeria monocytogenes in the food industry. However, the sensitivity of many of seafood-borne Listeria strains to phages has not been reported. This research investigated the host ranges of three listeriaphages (FWLLm1, FWLLm3 and FWLLm5) by the formation of lytic zones and plaques on host lawns and in vitro lysis kinetics of listeriaphage FWLLm3. The study also predicted the phage titres required to lyse host cells. The host ranges of the phages were determined using 50 L. monocytogenes strains, of which 48 were isolated from the seafood industry and two from clinical cases. Of the 50 strains, 36 were tested at 25 and 30 ℃ and the remainder (14) at 15 and 25 ℃. Based on the formation of either discrete plaques or lytic zones (host kill zones), the host ranges of FWLLm1, FWLLm3 and FWLLm5 were about 87%, 81% and 87%, respectively, at 25 ℃. Six L. monocytogenes strains from the seafood environment were insensitive to all three phages, while the other seafood strains (42) were phage-sensitive. The adsorption rate constant (k value) of listeriaphage FWLLm3 was between 1.2 × 10(-9) and 1.6 × 10(-9 )ml/min across four host strains in tryptic soy broth at 25 ℃. The cultures (at 3-4 log colony-forming unit (CFU/ml) were completely lysed (<1 log CFU/ml) when cultures were infected with FWLLm3 at > 8.7 log phage-forming units (PFU/ml) for 30 min. Re-growth of phage-infected cultures was not detected after 24 h. The effective empirical phage titre was similar to the calculated titre using a kinetic model. Results indicate the potential use of the three phages for controlling L. monocytogenes strains in seafood processing environments.

Virulence genes expression in viable but non-culturable state of Listeria monocytogenes in fish meat

“…Listeria monocytogenes is a gram-positive, facultative anaerobe, and non- sporulating pathogenic bacterium that causes listeriosis. L. monocytogenes is the second foodborne pathogen with the highest mortality rate (around 30%; Arachchi et al., 2014; Goulet et al., 2008). It is well documented that hly and inlA genes are important virulence genes in L. monocytogenes pathogenesis (Lindbäck et al., 2010).…”

Listeriaphages and coagulin C23 act synergistically to kill Listeria monocytogenes in milk under refrigeration conditions

“…Coagulin C23 is identical to coagulin A, a natural variant of the class IIa bacteriocin pediocin PA1/AcH (Hyronimus et al, 1998). FWLLm1 and FWLLm3 are myoviruses isolated from sheep faeces that infect strains of the species L. monocytogenes as well as other species such as Listeria ivanovii and Listeria welshimeri (Bigot et al, 2011;Arachchi et al, 2013). FWLLm1 was reported to immediately reduce 2.5 log 10 CFU/cm 2 a L. monocytogenes contamination after addition on the surface of vacuum-packed ready-to-eat chicken breast roll (Bigot et al, 2011) suggesting its potential for biocontrol of this pathogen in food.…”

Isolation and Characterization of Listeria monocytogenes Bacteriophages from Environmental Sources in Kars-Turkey

“…In the study they achieved 84.5% success in typing with the 100X routine phage test dilution and revealed that the repeatability of the typing was even higher after a few weeks. Arachchi et al (2014) have examined in their study the susceptibility of Listeria species previously isolated from sea products to unexplored bacteriophages. In a total of 50 Listeria strains, 42 strains were shown to be susceptible to phages.…”