Chalmers Agar, Modified, is used in microbiology for the selective isolation and identification of enteric pathogens such as Salmonella and Shigella from fecal specimens, particularly in cases of gastrointestinal infections. This medium inhibits the growth of non-pathogenic bacteria while supporting the development of target pathogens, allowing for clear visualization of colony morphology and growth characteristics. The modification improves selectivity and nutrient availability. It is commonly employed in diagnostic laboratories for public health surveillance, stool culture analysis, and microbiological research on infectious diseases.