Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which media is commonly used to culture a wound swab?

1. Mueller Hinton and chocolate agar

2. Hektoen and sheep blood agar

3. Chocolate and sheep blood agar

4. Selenite broth and chocolate agar

The correct answer is: Chocolate and sheep blood agar

The choice of chocolate agar and sheep blood agar for culturing a wound swab is based on their abilities to support the growth of a wide range of bacteria, particularly those that are commonly involved in wound infections. Chocolate agar is enriched and provides nutrients and growth factors that support the cultivation of fastidious organisms, including some strains of Haemophilus and Neisseria species. This medium has lysed red blood cells, which releases hemoglobin and other growth factors necessary for these bacteria, making it particularly useful for culturing specimens with complex microbial populations. Sheep blood agar, on the other hand, is used for the growth of a variety of organisms and helps to assess hemolytic activity. It’s particularly well-suited for isolating Streptococcus, Staphylococcus, and other common pathogens found in infected wounds. The presence of intact red blood cells allows for the observation of hemolysis patterns which can facilitate the identification of different bacterial species. Both media complement each other effectively, allowing for the broadest range of bacterial recovery from wound swabs, which can lead to a more accurate diagnosis and appropriate treatment. This combination reflects a standard practice in clinical microbiology, ensuring that both typical and fastidious pathogens can be isolated from wound specimens