Which medium is commonly used for the isolation of Enterobacteriaceae in clinical laboratories?

Which medium is commonly used for the isolation of Enterobacteriaceae in clinical laboratories?

• A. Bile-Escherichia agar.
• B. Nutrient agar.
• C. MacConkey agar.
• D. Blood agar.

Answer: (C)

MacConkey agar is commonly used for the isolation of Enterobacteriaceae in clinical laboratories due to its selective properties. This medium contains bile salts and crystal violet, which inhibit the growth of Gram-positive bacteria and promote the growth of Gram-negative bacteria, including the Enterobacteriaceae family. Furthermore, MacConkey agar differentiates among lactose fermenters and non-fermenters. Lactose fermenters, such as Escherichia coli, produce acid that lowers the pH of the medium, resulting in a color change that indicates their presence – typically appearing as pink colonies. Other media, such as nutrient agar, do not provide the selective or differential advantages necessary for isolating Enterobacteriaceae, as they support the growth of a broad range of microorganisms without differentiating between them. Blood agar, while useful for cultivating fastidious organisms, primarily supports the growth of bacteria and does not specifically target Enterobacteriaceae or offer differentiation. Bile-Escherichia agar is not commonly used in routine clinical laboratories for Enterobacteriaceae isolation, as MacConkey agar is the standard due to its proven reliability and functionality. Therefore, the attributes of MacConkey agar make it the appropriate choice for isolating and identifying Enterobacteri

MacConkey agar is commonly used for the isolation of Enterobacteriaceae in clinical laboratories due to its selective properties. This medium contains bile salts and crystal violet, which inhibit the growth of Gram-positive bacteria and promote the growth of Gram-negative bacteria, including the Enterobacteriaceae family. Furthermore, MacConkey agar differentiates among lactose fermenters and non-fermenters. Lactose fermenters, such as Escherichia coli, produce acid that lowers the pH of the medium, resulting in a color change that indicates their presence – typically appearing as pink colonies.

Other media, such as nutrient agar, do not provide the selective or differential advantages necessary for isolating Enterobacteriaceae, as they support the growth of a broad range of microorganisms without differentiating between them. Blood agar, while useful for cultivating fastidious organisms, primarily supports the growth of bacteria and does not specifically target Enterobacteriaceae or offer differentiation. Bile-Escherichia agar is not commonly used in routine clinical laboratories for Enterobacteriaceae isolation, as MacConkey agar is the standard due to its proven reliability and functionality. Therefore, the attributes of MacConkey agar make it the appropriate choice for isolating and identifying Enterobacteri