Prevalence, Pathogenicity, Virulence, Antibiotic Resistance, and Phylogenetic Analysis of Biofilm-Producing Listeria monocytogenes Isolated from Different Ecological Niches in Egypt: Food, Humans, Animals, and Environment

Abstract

Serious outbreaks of foodborne disease have been caused by Listeria monocytogenes found in retail delicatessens and the severity of disease is significant, with high hospitalization and mortality rates. Little is understood about the formidable public health threat of L. monocytogenes in all four niches, humans, animals, food, and environment, in Egypt. This study analyzed the presence of L. monocytogenes collected from the four environmental niches and bioinformatics analysis was implemented to analyze and compare the data. PCR was used to detect virulence genes encoded by pathogenicity island (LIPI-1). prfA amino acid substation that causes constitutive expression of virulence was common in 77.7% of isolates. BLAST analysis did not match other isolates in the NCBI database, suggesting this may be a characteristic of the region associated with these isolates. A second group included the NH1 isolate originating in China, and BLAST analysis showed this prfA allele was shared with isolates from other global locations, such as Europe and North America. Identification of possible links and transmission pathways between the four niches helps to decrease the risk of disease in humans, to take more specific control measures in the context of disease prevention, to limit economic losses associated with food recalls, and highlights the need for treatment options.

Keywords: L. monocytogenes; animals; antimicrobial and virulence genes; bioinformatics analysis; food; humans; prfA phylogenetic analysis.

Figure 1

Individual isolates showing hierarchical clustering of isolates and factors. Binary factors (such as antibiotics or genes) indicating presence as green (relative response 1) or absence as red (relative response 0). Clustering is based on Wald-like test (D₂) and for binary data.

Figure 2

Protein alignment of prfA protein from L. monocytogenesisolates. Alignment was made to prfA from Listeria monocytogenesstrain NH1 (Genebank: GCA_002969195.1). Differences to NH1 are highlighted and can be found in Table 1.

Figure 3

Correlation matrix of virulence and antibiotic resistance profiles that were different among the recovered Listeria monocytogenes. Only correlations that were significant (p < 0.05) are represented in the matrix.

Figure 4

Principle component analysis of factors and relationship with serotype and individual isolates.

Figure 5

Phylogenetic analysis of prfA gene sequences among isolates in this study. Node size indicates proportion of isolates sharing a specific genotype.