Detection of Salmonella spp. in Hamburgers: a Comparison Between Modified Standard and Salmosyst Methods

Salmonella spp. was analyzed in beef and chicken and in beef hamburgers using two different microbiological methods with slight modifications in the biochemical test stage. Of the 80 hamburger samples analyzed, 22 (27.5%) were positive for Salmonella spp., 10 (12.5%) beef and 12 (15%) chicken and beef hamburgers. Of the 22 positive samples, 11 (50.0%) were detected by the standard method alone, 5 (22.73%) by the Salmosyst method, and 6 (27.27%) were detected using both methods. Sensitivity and specificity of methods was investigated. The standard method was the most effective to identify real positive results, while Salmosyst method afforded to characterize real negative results. As for accuracy, both methods were acceptable to analyze Salmonella spp. in hamburgers. The importance of streaking Salmonella spp. colonies obtained using the TSI and LIA agars, with atypical characteristics 1 and 2 was also revealed, since these two sets of characteristics may be used to isolate atypical Salmonella spp. serotypes, which ferments lactose and Salmonella Parathyphi, which does not decarboxylate lysine, respectively. Secondary screening was efficient as regards the differentiation between Proteus spp. and Salmonella spp. colonies.