Which agar is the medium of choice for the isolation of Yersinia strains from stool specimens?

Which agar is the medium of choice for the isolation of Yersinia strains from stool specimens?

• A. Salmonella-Shigella agar
• B. Hektoen enteric agar
• C. MacConkey agar
• D. CNA agar

Answer: (C)

The medium of choice for the isolation of Yersinia strains from stool specimens is MacConkey agar. This agar is specifically designed for the isolation of gram-negative bacteria, such as Yersinia, and differentiates lactose fermenters from non-fermenters based on their ability to utilize lactose. MacConkey agar contains bile salts and crystal violet, which inhibit the growth of gram-positive organisms, allowing for the selective growth of Enterobacteriaceae. Yersinia enterocolitica, the primary pathogen of the Yersinia genus associated with enteric infections, does not ferment lactose and will produce colorless colonies on this medium, making it easier to identify among other non-lactose fermenters. While other agars like Salmonella-Shigella agar and Hektoen enteric agar can also isolate Yersinia and differentiate between various enteric bacteria, MacConkey agar is the most suitable for directly isolating Yersinia strains specifically from stool specimens due to its selective properties and the ability to clearly differentiate lactose fermenters from non-fermenters. CNA agar, on the other hand, is selective for gram-positive bacteria and would not be appropriate for isolating Yersinia strains.

The medium of choice for the isolation of Yersinia strains from stool specimens is MacConkey agar. This agar is specifically designed for the isolation of gram-negative bacteria, such as Yersinia, and differentiates lactose fermenters from non-fermenters based on their ability to utilize lactose.

MacConkey agar contains bile salts and crystal violet, which inhibit the growth of gram-positive organisms, allowing for the selective growth of Enterobacteriaceae. Yersinia enterocolitica, the primary pathogen of the Yersinia genus associated with enteric infections, does not ferment lactose and will produce colorless colonies on this medium, making it easier to identify among other non-lactose fermenters.

While other agars like Salmonella-Shigella agar and Hektoen enteric agar can also isolate Yersinia and differentiate between various enteric bacteria, MacConkey agar is the most suitable for directly isolating Yersinia strains specifically from stool specimens due to its selective properties and the ability to clearly differentiate lactose fermenters from non-fermenters. CNA agar, on the other hand, is selective for gram-positive bacteria and would not be appropriate for isolating Yersinia strains.