Whole-Genome Sequence Profiling of Listeria innocua From Different Sources: Implications for Public Health

Foodborne disease outbreaks, particularly those associated with antimicrobial-resistant (AMR) bacterial pathogens, have become an issue of severe public health concern owing to increased globalisation and active food trade among countries. These disease outbreaks include listeriosis, which can cause notable complications such as diarrhoea, headaches, and vomiting. The data generated during the South African foodborne outbreak caused by AMR Listeria monocytogenes led to the inclusion of listeriosis on the South African list of mandatory notifiable medical conditions. Prospective solution to managing the increasing threat caused by AMR foodborne pathogens to humans require frequent surveillance of food products using techniques with high throughput and discriminatory potential. Thus, this study assessed the virulome, resistome, and phylogenetics of two Listeria innocua strains (LIN_NWU_CNKT and LIN5_NWU_CNKT) previously isolated from food and water samples collected in the North-West Province, South Africa, using whole-genome sequencing (WGS). Based on WGS analysis, the isolates were confirmed as L. innocua, with genomes that are closely related to previously isolated human pathogens. The genomes of these two isolates harboured virulence genes, including those responsible for adherence (fbpA, inlJ), invasion (aut, inlA), and immune modulation (inlC, lntA). In addition, the genes encoding antibiotic resistance were found in the genomes. These genes confer resistance to antibiotics such as phosphonic acid (fosX), lincosamide (lin), tetracycline (tetM), and glycopeptide (vanT). These findings highlight a crucial need to enforce standard operating procedures in food processing to reduce the spread of AMR and foodborne outbreaks.