Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:…et al., 2011), in the virulence
of some bacteria like extraintestinal pathogenic E. coli strains,
Edwardsiella tarda, or Salmonella typhimurium and plays a role
in the biosynthesis of antibiotic and toxins (Dang et al., 2011;
Garcie et al., 2016; Verbrugghe et al., 2015; Vivien et al., 2005).
Category: