Is it true that an e-coli infection be caused by a blood transfusion?

Maybe-not probable.: The e coli is most likely from a urinary tract infection (UTI) or from gut infection through contaminated meat, etc. Transfusion is a rare cause for any infection, but if it happens, it is usually with yersinia or some other bacteria, etc., though an e. Coli infection is possible, especially if there is an unclean environment, and the transfused product had an infection or was not well preserved.

Doesn't happen: E. Coli is unlikely to contaminate blood because it isn't usually on the skin, and it does not like to grow at the temperature at which the blood is stored. A unit of red cells laced with e coli would turn green or purple and be discarded. This is in contrast to the skin staph that occasionally infect platelets, which mus be stored at room temperature.