The following 5 microbial agents are the most common for causing food poisoning in developed nations:
1. Campylobacter, which is common in chicken
2. Clostridium, often occurs in foods that have been warmed, then cooled then re-heated
3. Escherichia coli (E-coli) found in the lower GIT, often a sign of fecal pollution in the waterways
4. Listeria, often found in the environment, eg. soil and water. Very tough, can thrive in conditions as hot as 50 degrees and as low as 1, and causes septicemia
5. Salmonella, a common cause of food poisoning, S&S of salmonella poisoning include: stomach pain, diarrhea, chills, fever or headache (normally for around 3-5 days)
Good handwashing and basic food preparation concepts alleviates the spread of most of these causes of food poisoning.