Question

Sodium thiosulfate is often added to selective culture media to

a) Inhibit gram-negative bacteria
b) Neutralize acids
c) Promote anaerobic growth
d) Inactivate antibiotics

Answer 1

Sodium thiosulfate is added to selective culture media to inactivate antibiotics, ensuring that bacteria sensitive to the antibiotics can still grow and be detected in clinical specimens.

Step-by-step explanation:

Sodium thiosulfate is incorporated into certain selective culture media to serve as a reductive agent. Its primary role in this context is to inactivate antibiotics such as penicillin and streptomycin which may be present in clinical specimens and would otherwise inhibit bacterial growth, skewing the results of the culture. It achieves this by reducing these compounds, thus neutralizing their antibacterial effect and allowing even those bacteria sensitive to the antibiotics to grow and be detected. Since antibiotics are designed to prevent the proliferation of bacteria, eliminating their influence is vital for a successful culture of the microorganisms that are targeted for study or clinical diagnosis.