Non-O1/non-O139 Vibrio cholerae (NOVC) is a natural inhabitant of aquatic ecosystems. It can cause both intestinal and extraintestinal infections in humans through the consumption of contaminated food or direct contact with contaminated surfaces, such as seawater or sediment. Previous studies have identified virulence-associated genes in NOVC that may contribute to its ability to cause infections. This doctoral thesis aimed to characterize the virulence mechanisms of NOVC isolated from food and environmental sources. A literature review was conducted to explore the infection routes of NOVC and its virulence-associated gene profiles. The genes were then compared with whole genome sequences of NOVC isolates from seafood (63 strains) and the German sea coastline (31 strains) to determine the presence of virulence-associated genes. Phylogenetic analysis was also performed. Additionally, phenotypic tests, including biofilm formation, hemolytic activity, motility, and serum resistance, were carried out to further validate the genetic findings. The antimicrobial resistance (AMR) of NOVC was also examined at both the genetic and phenotypic levels. Virulence-associated genes were classified into five stages, representing the infection process from ingestion to detachment from the human host. Most of these genes were detected in NOVC isolates from both food and environmental sources, including key toxin-encoding genes (hlyA, rtxA, chxA, stn), pathogenicity islands (VPI-2 and VSP-2), and secretion systems (T3SS and T6SS). A close core genome relationship was observed between the NOVC strains in this study and clinical NOVC strains. Notably, all NOVC strains exhibited increased motility at 37°C compared to 25°C, and most were capable of forming strong biofilms at both temperatures. All strains showed hemolytic activity against both human and sheep erythrocytes, but only a small subset of (6%) NOVC could survive in 60% human serum. In antimicrobial susceptibility tests, five NOVC strains developed non-wildtype resistance to antimicrobials across three different classes (penicillin, carbapenem, cephalosporin). In conclusion, this study characterized the virulence profiles of NOVC isolates from seafood and German coastal waters, highlighting the need for further monitoring and research.
