Bacteria or toxins produced by bacteria are often the cause of foodborne ailments. Some examples are:

Salmonella
It is often found in raw eggs and poultry. Symptoms include stomach pain, diarrhea, chills, nausea, vomiting and fever. Salmonella can be prevented by cooking eggs to at least 63 degrees Centigrade and poultry at 74 degrees Centigrade or higher. Use pasteurized egg products if possible.

Staphylococcus aureus
Carried in the hands, face, and nose of most healthy people, this bacteria itself is not harmful. It is the toxin that the bacteria produces, when allowed to grow in food, that causes illness in people. The poison is very powerful and cannot be destroyed by cooking or freezing. To prevent intoxication by this bacteria, keep hot foods hot (57°C or higher) and cold foods cold (5°C or lower).

E. coli
It is found on the surfaces of beef, sometimes fish and in non-pasteurized fruit and vegetable juices. One can control this type of bacteria by cooking ground meat to a minimum of 68°C for at least 15 seconds.