Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam 2026 - Free Medical Laboratory Science Practice Questions and Study Guide

For culture and sensitivity testing of a urine specimen, MacConkey and sheep blood agar are commonly used due to their ability to effectively isolate and identify urinary pathogens.

MacConkey agar is selective for Gram-negative bacteria, as it inhibits the growth of Gram-positive bacteria due to its bile salts and crystal violet content. It also differentiates lactose fermenters, which can be useful in identifying pathogens like Escherichia coli, a common cause of urinary tract infections. The ability of MacConkey agar to provide both isolation and differentiation makes it an ideal choice for urine specimens.

Sheep blood agar, on the other hand, is a rich, non-selective medium that supports the growth of a wide variety of bacteria. It allows for the observation of hemolytic activity, which is valuable in identifying certain pathogens that may cause urinary tract infections. The combination of these two media enhances the likelihood of isolating the relevant pathogens and determining their sensitivity to various antibiotics, hence playing a vital role in culture and sensitivity testing for urine samples.