What is the primary reason sodium polyanethol sulfonate is used as an anticoagulant in blood cultures?

Sodium polyanethol sulfonate (SPS) is primarily utilized in blood cultures for its anticoagulant properties and its ability to create an optimal environment for the growth of bacteria. The correct answer emphasizes two key functions of SPS: preventing phagocytosis and neutralizing the bactericidal effect of human serum.

By preventing phagocytosis, SPS helps to protect the bacteria in the blood culture from being engulfed and destroyed by immune cells, such as neutrophils. This is crucial for accurate microbial detection, as any viable bacteria need to remain intact and proliferate for them to be identified correctly.

Additionally, SPS neutralizes the bactericidal effects of human serum, which can limit the growth of bacteria. Human serum contains various components that can inhibit bacterial growth, including antibodies and complement proteins. SPS helps to mitigate these effects, ensuring that the bacteria have a better chance to thrive and be detected in the culture.

These combined actions make SPS an effective component in blood culture systems, enhancing the likelihood of recovering pathogenic microorganisms present in the sample.