Five serovars of Salmonella spp. (S. Montevideo BAA 710, S. Newport BAA 707, S. Saintpaul ATCC9712, S. Typhimurium
ATCC14028 and S. Agona BAA 707) previously adapted to 100 mg/ml nalidixic acid (SigmaeAldrich, St Louis, MO, USA) were used in this study