OSMT (Ontario Society of Medical Technologists) Practice Exam

What is the most commonly added enrichment to media?

1. Peptic digest blood

2. Haemolysed blood

3. Fresh human blood

4. Laked blood

5. Warmed animal blood

The correct answer is: Warmed animal blood

The most commonly added enrichment to culture media is the use of warmed animal blood. Blood serves as a source of nutrients, such as proteins and amino acids, essential for the growth of various microbial organisms. The warming process helps to ensure the blood is at a suitable temperature for promoting bacterial growth while maintaining its liquid state, allowing for better incorporation into the media. Blood enriches the media by providing growth factors and supports the cultivation of fastidious organisms, which have complex nutritional requirements. This practice is commonplace in microbiological diagnostics and research to enhance the recovery of pathogenic bacteria that thrive in blood-rich environments. In contrast, peptic digest blood, haemolysed blood, laked blood, and fresh human blood may all have specific applications but are not as widely used in general media enrichment as warmed animal blood. For example, peptic digest blood is a form of blood that has been treated to break down proteins, which is useful in certain formulations but not as common as animal blood. Haemolysed blood and laked blood may be more specific to selective media for certain organisms, while fresh human blood tends to be less utilized due to ethical and practical considerations in laboratory settings.