Which additive would be found in a yellow topped tube?

The yellow topped tube typically contains Sodium Polyanetholesulfonate (SPS), an additive primarily used for blood culture collections. SPS is known for its ability to inhibit the activity of certain antibiotics, which is crucial when testing for microorganisms in blood samples. This characteristic allows for a more accurate culture by preventing the antibiotics from interfering with the growth of pathogens that may be present in the blood.

In blood cultures, it is vital to create an optimal environment for the growth of bacteria or fungi, and the presence of SPS aids in achieving this by reducing the likelihood of false-negative results. Therefore, the use of SPS in yellow topped tubes makes them uniquely suited for microbiological testing, separating them from tubes with different additives that serve other diagnostic purposes.