Separate venipunctures were performed to collect three sets of blood cultures from a patient with an artificial heart valve.The first and third sets grew a gram-positive pleomorphic rod in 1 of 2 bottles while the second set had no growth in either bottle.What is the most likely explanation for these findings?

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It is important to remember that even though antiseptic technique is used in the collection of blood, somewhere between 1% and 3% of blood cultures become contaminated with organisms such as coagulase-negative staphylococci, Corynebacterium spp., Bacillus spp.(not B.anthracis), alpha-hemolytic streptococci, and Propionibacterium acnes, which are ordinarily skin colonizers, resulting in pseudobacteremia.

Separate Venipunctures Were Performed to Collect Three Sets of Blood