How do bacteria get into food?

Multiple ways: Bacteria may be introduced to food anywhere from the farm, to any processing or from contamination at the final food preparation at the kitchen.

Food contamination: can result from washing even "organic" produce with water contaminated by animal manure or by other contact with animals. Another source is when a food handler fails to wash his hands. Inadequate food preparation at home or at a restaurant is another way that food can become contaminated. Food that is old such as left overs, even if refrigerated, can breed microbes. "When in doubt, throw it out!"