Types

• Common bacteria that may contaminate food include E coli, salmonella and staph (staphylococcus aureus). These bacteria, and many others, cause food poisoning.
  Seafood, undercooked poultry and undercooked red meat often harbor harmful bacteria--other foods, such as vegetables, may also harbor these bacteria through cross contamination.
  
  

Hands

• The hands are one common way food becomes contaminated with bacteria, especially E coli and staph. E coli may be present on the hands for a number of reasons, but not washing after using the bathroom is one potential reason. Staph is present in many wounds, and on the skin, and according to the Texas Agriculture Extension Service, in the respiratory passages of nearly half the human population. Unless you wash your hands, it is possible that you will contaminate food you handle.
  
  

Utensils

• Cooking utensils may contaminate food with bacteria. This occurs easily if the utensil was used on a raw item (a knife used on raw chicken, for example) and then used on fresh produce items (such as head lettuce). Washing the utensil can prevent this. However, insufficient washing may allow the bacteria to remain, and flourish, on the utensil--making it a potential source of contamination.
  
  

Cutting Boards And Counter Tops

• Improperly sanitized cutting boards or counter tops (from insufficient cleaning) may harbor harmful bacteria. When the cook prepares food on these surfaces, bacteria may contaminate food.
  
  Cutting boards and counters may be exposed to bacteria during food preparation--this usually occurs if they are used as cutting surfaces for raw meat; if the surface is not washed well, the bacteria may thrive.
  
  Pets walking on countertops may track bacteria onto the surface.
  
  

Contamination of Soil or Water

• In 2006, the United States experienced an outbreak of E coli traced to bagged spinach. The FDA's investigation into the cause was inconclusive; however, it suspected that animal fecal matter containing the bacteria may have been in nearby waterways and soil.
  This source of bacterial contamination is not, of course, limited to farms. Bacteria naturally exist in the backyard garden too--all produce, whether you grew it yourself or bought it at the supermarket, should be washed before being eaten or cooked,
  
  

Industrial

• Food packaging plants must adhere to strict sanitation standards--otherwise, they may become a source of contamination. Such was the case with peanut butter contaminated with salmonella in 2007. According to "Peanut butter contamination pinned on moisture," at usatoday.com, ConAgra foods determined that a moisture problem (from a leaking roof) led to salmonella contamination of peanut butter at a food manufacturing plant.
  
  

Considerations

• Foods that will be eaten raw (such as lettuce, tomato and other salad items) should be washed well before eating and should be kept away from raw meats.
  
  Washing your hands is one way to prevent accidental contamination of food while cooking or eating.