It is the cause of an estimated 1.4 million illnesses annually in the United States ( 25). Salmonella has been associated with many food-borne diseases across the world ( 19). On the basis of its good specificity, XA medium is useful for the isolation of Salmonella spp. The specificity of XA medium (92.0%) was superior to that of XLD (73.0%), with a total of 14 and 47 false-positive results found on XA medium and XLD, respectively. The sensitivities of XA medium and XLD were equal (100%), and a total of 6 Salmonella strains were isolated from the 180 food samples. In the second phase of the study, a total of 180 food samples were cultured onto XA medium and XLD after selective enrichment.

mirabilis appeared as black colonies on XA medium. Citrobacter freundii ( n = 21) and Proteus mirabilis ( n = 21) stock cultures produced black colonies on XLD, whereas only 4 strains of P. The sensitivities of XA medium and XLD were identical (92.7%).

The remaining 6 strains belonged to Salmonella enterica serovars Berta ( n = 1), Paratyphi A ( n = 1), Gallinarum ( n = 2), and Pullorum ( n = 2). tested, 76 produced a characteristic black colony on XA medium and XLD. XA medium and XLD were evaluated with a total of 82 Salmonella and 69 non- Salmonella stock cultures. The sensitivity and the specificity of XA medium were compared to those of xylose lysine desoxycholate agar (XLD) using stock cultures and naturally contaminated food samples. We describe an improved selective, differential, and cost-effective medium, XA medium, which contains d-arabinose, to facilitate the selective isolation of Salmonella spp.

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