Evaluation of Teknaf Enteric Agar (TEA): A modified MacConkey's Agar for the isolation of Shigella dysenteriae type 1 and Shigella flexneri[brief report]

Abstract

To develop a better and selective medium for the isolation of Shigella spp., MacConkey's Agar (MAC) was modified by adding potassium tellurite (K2TeO3) at a concentration of 1 microgram/ml. The formulation designated Teknaf Enteric Agar (TEA) was studied for the inhibitory effect of potassium tellurite on the growth of different enteric bacteria, and as a medium for isolating Shigella spp. from clinical stool samples (n = 3125). We observed that the growth of E. coli was effectively inhibited on TEA with no effect on the growth of S. dysenteriae type 1 and S. flexneri. A total of 2019 Shigellae were isolated through the combined use of TEA, MAC, and Salmonella-Shigella Agar (SS). On TEA, 1921 S. dysenteriae type 1 and S. flexneri were isolated as compared to 1765 from the combined use of MAC and SS. A total of 194 of S. dysenteriae type 1 and S. flexneri were exclusively isolated from TEA as compared to 38 which were only made from MAC and SS. We conclude that TEA significantly increased the overall isolation rate of Shigella spp. as compared to the combined use of MAC and SS (P < 0.0001), although it is not suitable for the isolation of S. sonnei