Which organism has not been implicated in bacterial contamination of donor blood products?

• A. Escherichia coli
• B. Yersinia enterocolitica
• C. Citrobacter freundii
• D. Pseudomonas putida

Answer: (B)

Bacterial contamination of donor blood products is most often linked to organisms that routinely inhabit the human gut or the environment and can survive or multiply during storage conditions. Escherichia coli, Citrobacter freundii, and Pseudomonas putida are commonly cited as contaminants in stored blood products and have been linked to septic transfusion reactions. Yersinia enterocolitica, while capable of causing infection, is less frequently reported as a donor blood contaminant, making it the best choice for an organism not typically implicated in this context. This reflects how the prevalence of certain bacteria in the transfusion setting guides which organisms are most often associated with contaminated products.