Final answer:
The doughnut contamination incident in 1996 was caused by Salmonella contamination. The contaminated food item associated with the outbreak was bread.
Step-by-step explanation:
The doughnut contamination incident in 1996 relates to a foodborne disease outbreak caused by Salmonella contamination. A case-control study was conducted, and it was determined that the contaminated food item associated with the outbreak was bread. The incident led to legislation aimed at preventing adulteration of bread with unapproved substances.