What is the most common cause of blood culture contamination?

The most common cause of blood culture contamination is improper skin preparation. This step is crucial because the skin is home to various microorganisms, and if it is not adequately disinfected before blood is drawn, these bacteria can enter the sample and lead to false-positive results. Proper skin antisepsis—typically involving the use of alcohol or chlorhexidine—helps to minimize the risk of contaminating the blood culture with normal skin flora.

While the other options can contribute to issues with blood cultures, they are not as prevalent as improper skin preparation. Contaminated equipment can introduce pathogens, and incorrect storage or delayed transport may affect the viability of the organisms but are less likely to be the source of contamination than the initial skin preparation.