The current edition of The Journal of Food Protection reports on another study into three outbreaks involving romaine lettuce contaminated with Shiga toxin-producing Escherichia coli.  This one focuses on determining the source of the outbreak vehicle through traceback investigations.  The Food and Drug Administration personnel traceback investigation experts employ a standardized process to initiate, execute, and interpret the results of traceback investigations in collaboration with the Centers for Disease Control and Prevention and state and local…