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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Egg and Poultry Production Safety Research Unit » Research » Publications at this Location » Publication #413809
Research Project: Reduction of Foodborne Pathogens and Antimicrobial Resistance in Poultry Production Environments

Location: Egg and Poultry Production Safety Research Unit

Title: Deciphering selective pressures: comparative genomics and phylogenetic analyses of four virulence factors in Listeria monocytogenes isolates linked to chicken consumption in the United States.

Author
item Li, Xiang
item Oladeinde, Adelumola - Ade
item Rothrock, Michael
item ISHII, SATOSHI - University Of Minnesota
item SHEN, CANGLIANG - West Virginia University

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/28/2024
Publication Date: 7/15/2024
Citation: Li, X., Oladeinde, A.A., Rothrock Jr, M.J., Ishii, S., Shen, C. 2024. Deciphering selective pressures: comparative genomics and phylogenetic analyses of four virulence factors in Listeria monocytogenes isolates linked to chicken consumption in the United States. Poultry Science Association Meeting Abstract. PSA Annual Meeting.

Interpretive Summary: N/A

Technical Abstract: Foodborne pathogens, including Salmonella, Shiga toxin–producing Escherichia coli (STEC), and Listeria, pose substantial challenges to the food industry. Of particular concern is Listeria monocytogenes, exclusively pathogenic to humans, prompting a zero-tolerance policy in U.S. food products. While current classification relies on cell wall antigen expressions, comprehensive genomic characteristics and virulence factors remain insufficiently explored. In this study, we conducted an analysis of 36 L. monocytogenes (LM) complete genomes. The genomes were retrieved from the NCBI Pathogen Detection Database and encompassed 20 environmental and 16 clinical LM isolates. Our whole-genome phylogeny revealed distinct separations among strains from different geographic locations, despite some environmental and clinical samples clustering together. In addition, we further compared the unrooted phylogenetic trees of virulence factors of Listeriolysin O (LLO, under exotoxin category), phospholipase C (PlcB, exotoxin), inner-membrane chaperone DF (SecDF, secretion system), and membrane-bound SPases Z (SipZ, secretion system). The results exposed notable conflicts in topological distances. Further aligning the codons and employing a fixed-effects likelihood model based on Chi-squared statistics, we delved into selective pressures on all four-virulence factor genetic codons. We found that that codons with over 60% sequence similarity were under neutral selection (the organisms that are more adapted to environment are more likely to survive), with SecDF standing out with three purifying selection (reduces the genetic diversity by removing deleterious alleles) codons. In summary, our results underscore the stability of the majority of LLO, SipZ, SecDF, and PlcB virulence factor codons in U.S. chicken-associated LM isolates. Notably, the identifications of three purifying selection codons in SecDF may limit the efficacy of drugs used for treating listeriosis.