Whole Genome Sequence Analysis of Phage-Resistant Listeria monocytogenes Serotype 1/2a Strains from Turkey Processing Plants

Abstract

Listeria monocytogenes is a Gram-positive bacterial pathogen and the causative agent of listeriosis, a severe foodborne infection. L. monocytogenes is notorious for its ability to persist in food processing environments (FPEs) via a variety of adaptive traits. Even though traits such as cold tolerance, biofilm formation and sanitizer resistance have been extensively investigated for their roles in persistence of L. monocytogenes in FPEs, much less is known about resistance to bacteriophages. Previous studies explored phage resistance mechanisms in laboratory-created mutants but it is imperative to investigate phage resistance that is naturally exhibited in FPE-derived strains. Here, we integrated the analysis of whole genome sequence data from a panel of serotype 1/2a strains of sequence types 321 and 391 from turkey processing plants, with the determination of cell surface substituents required for phage adsorption and phage infection assays with the four wide-host-range phages A511, P100, 20422-1 and 805405-1. Using a specific set of recombinant phage protein probes, we discovered that phage-resistant strains lacked one or both of the serogroup 1/2-specific wall teichoic acid carbohydrate decorations, N-acetylglucosamine and rhamnose. Furthermore, these phage-resistant strains harbored substitutions in lmo1080, lmo1081, and lmo2550, which mediate carbohydrate decoration of the wall teichoic acids.

Harnessing Whole Genome Sequence Data for Facility-Specific Signatures for Listeria monocytogenes: A Case Study With Turkey Processing Plants in the United States

“…The ST321 strains from Plant A and Plant B harbored the T730 inlA PMSC, as also reported previously (Brown et al, 2021). ST321 isolates from a variety of sources have been previously reported to harbor inlA PMSCs, but in other locations.…”

“…We found that inlA PMSCs were ST-specific and not randomly distributed among the sequenced FPE strains. Specifically, they were only encountered in seven of the nine strains of ST5 (serotype 1/2b; T635) and, as previously reported (Brown et al, 2021), in all six ST321 strains (serotype 1/2a; T730) (Supplementary Table 1; Figure 2).…”

“…Phage susceptibility assays were done at 25 • C as described previously using the wide-host-range lytic phages A511, P100, 20422-1, and 805405-1 (Brown et al, 2021). Resistance to BC and cadmium was determined as described previously (McLauchlin et al, 1997;Mullapudi et al, 2008).…”

“…ST321 strains constitute an especially attractive model system to showcase plant-specific genomic markers, because, in addition to the six strains from the turkey FPEs, ST321 strains have been investigated extensively from an unrelated type of FPE, i.e., a salmon processing plant (Harrand et al, 2020), as discussed above. In addition, ST321 is emerging as a dominant ST among food and FPE-derived isolates of L. monocytogenes (Hurley et al, 2019;Harrand et al, 2020;Matle et al, 2020;Cooper et al, 2021) and is noteworthy for high prevalence of BC resistance (Brown et al, 2021;Cooper et al, 2021). Therefore, ST321 strains from the turkey and salmon FPEs (Harrand et al, 2020) and other sources were investigated further for genomic content in a specific chromosomal hotspot located between lmo301 and lmo305 (Lee et al, 2012).…”

“…Furthermore, the serotype 1/2a and 1/2b strains were also frequently resistant to three wide-host-range lytic phages, including two phages isolated from environmental swabs from the same turkey processing plants (Kim et al, 2008). Recently, phage resistance of some of these turkey processing plant-derived strains of ST321 and ST391 was further characterized via WGS analysis and investigation of phage receptors on the teichoic acid of the cell wall (Brown et al, 2021).…”