The three tested bacterial strains were obtained from the Culture Collection at the University of Gothenburg: Staphylococcus aureus CCUG 1828, Escherichia coli CCUG 10979, and Listeria monocytogenes CCUG 15527. A test culture was prepared by growth on MH agar overnight, and colonies were diluted to a 0.5 McFarland in MH broth.