9. The pure culture of suspected Shigella sp.was inoculated in the Kligler iron agar .Which of the following are possible results of Shigella sp growth after 18 h incubation? 1. red butt 2.yellow slant 3. black dots in the butt 4. yellow butt

The correct answer is:<br /><br />3. black dots in the butt<br /><br />Explanation:<br /><br />Shigella species are known to be lactose non-fermenters. When inoculated on Kligler iron agar, they do not ferment lactose, which would result in a yellow color. Instead, they utilize other sugars present in the medium and produce hydrogen sulfide (H2S). The production of H2S leads to the formation of black dots or colonies in the butt of the agar. Therefore, the presence of black dots in the butt indicates the growth of Shigella sp. after 18 hours of incubation.