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What bacteria causes food poisoning

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What bacteria causes food poisoning

Illness related to food contamination has become common these days. However it can be prevented with proper care and maintenance of food products. It is assessed that around 24 to 84 million cases related to food borne diarrhea arise every year in the United States, which costs around $5 to $17 billion dollars in treating with proper medical care and lose in economic productivity.

What bacteria causes food poisoning

Food borne diseases can also be caused by chemicals induced in the products, presence of heavy metals in food, interaction of pathogens, fungi, viruses and bacteria. Although the food borne disease arise maximum by activity of bacteria in the food. But it is also a fact that less than 20 bacterial species are involved in the contamination of food rather than the whole bacterial colony. Out of which, more than 90 percent cases are due to Staphylococcus aureus, Clostridium pefrigens, Camplylobacter and many more strains of bacteria. These can be easily found on raw food products. Usually large number of bacteria are present to cause food poisoning illness.

However, it can be prevented by:

  1. Controlling the number of bacteria present in the food products
  2. Prevent the small number of bacterial colony to grow
  3. Degrade and eliminate bacteria by cooking at high temperature.
  4. Preserve food properly so that re-contamination cannot be occurred.

Reasons for Contamination of food

Poor hygiene, poor cleaning of preparation and storage areas of food and improper cleaning of utensils where the food is prepared can cause major contamination of raw and cooked food. Improper and careless handling of raw and cooked foods can allow food poisoning bacteria to grow. The optimal temperature in which the bacteria grow best is around 40-140 degree Fahrenheit (5 degree C). Any food should not be kept in any open or danger zone for necessary longer. Serious food poisoning illness can directly be caused by undercooking or improper making of home canned food.

As we know food poisoning bacteria are mainly present on many foods and they tend to contain some characteristic features of bacteria which requires an effective control method.

What bacteria causes food poisoning

1. Staphylococcus aureus

Staphylococcus aureus are the bacterial species that commonly found in skin, severe wounds and respiratory system of human. S.aureus produce a toxin that cause illness leading to food poising in human beings. However, cooking at high temperature destroys the bacterial but the toxin produced is heat resistant a scan tolerate heat stress and may not be destroyed. This bacteria strain commonly found in foods that are hand prepared such as potato salad, sandwich spread and ham salad. If you leave these kind of food at room temperature, S.aureus will grow instantly and produce the toxins.

Source of bacteria

Staphylococcus aureus can easily be present on skin that can contaminate the food if the hand is not washed properly. The foods like raw meat, chicken, pastries, puddling are especially in danger of getting contaminated by Staphylococcus aureus as they are not cooked.

Incubation period and duration of illness is 30 to 8 hours and about one day of illness respectively.

Symptoms of Food posioning due to S.aureus are nauseated, vomiting, stomach ache, and sometimes diarrhea too.

How to reduce them?

Drink fluids and water as much as you can to keep to hydrated and if you cannot drink enough fluids, consult your doctor to prescribe you some medication for nausea and diarrhea.


  • You can prevent the bacteria by keeping good personal hygiene while preparing food will keep S.aureus away from your food.
  • Keep the raw a cooked food in refrigerator that will prevent the growth of the bacteria if there is present any. Use container to keep food in the refrigerator within 2 hours of cooking.
  • Cook food at optimum temperature for that use of food thermometer. Also preserve hot food as hot and cold food as cold.

2. Salmonella

The Salmonella bacteria are present in gastrointestinal tracts of animals and humans. Salmonella commonly found in protein rich foods such as meat, fish, chicken and eggs. Additionally, if any food that have grown salmonella colony which have contaminated the food is then kept at improper temperature can cause Salmonellosis.

Salmonella are only destroyed at more than 150 degree Fahrenheit. Salmonellosis can majorly cause by the contamination of cooked foods and improper cooking of food.

Source of bacteria

There are variety of food that can be associated with Salmonella such as vegetables, chicken, meat, pork, fruits and many more.

Incubation period to grow the bacteria is 6 hours to 6 days and duration of illness ranges from 4-7 days.


Start to stomach ache, vomiting, fever and diarrhea.


  • Contamination in food can be occurred by improper washing and cleaning of utensils or in surface contact of uncleansed utensils after washing of raw food products.
  • Use of refrigerator for food preservation can prevent the contamination of raw and cooked food.
  • Wash your hands after the contact with animals like chicken, birds, reptiles, their food or their surroundings.

3. Enteropathogenic Escherichia.coli

E.coli is the main cause of diarrhea in developing countries and cities encountering poor sanitation. E.coli is linked with Traveler’s diarrhea in the United States. There was a recent outbreak of E.coli in a nursing home in Ontario, North America. It was a severe outbreak of E.coli associated with hemorrhagic colitis.

Source of the bacteria could be the feces of infected humans, also some reservoirs of animals. Contamination of food is probably due to feces and untreated water.


  • Avoid use of contaminated cooked meat equipment for preparing fresh food, water or handling of food by infected person.
  • Improper and adequate cooking of food should be avoided.
  • Avoid consuming high dangered food like undercooked beef, unpasteurized milk, melted cheese prepared from unpasteurized milk, or sprouts.
  • Use food thermometer to cook ground beef at optimum temperature of 160°F for safe consumption.
  • Always wash hands before or in between and after making food, after changing the diapers of infants, and after being in contact with animals like cow, cattle, sheep, goats or their food or their surroundings.

Incubation period of E.coli is 3-4 days for normal people but it can range between 1-10 days for several people.

Duration of illness is 5-10, most people get better after this time period but if somehow, HUS develops, it starts showing symptoms after 1 week. After that several days would be fine to get better.

Symptoms can be severe diarrhea that can be bloody sometimes, stomach cramps and vomiting can occur. There might be fever or not.

Severe illness due to E.coli can cause HUS (Hemolytic uremic syndrome) lead to less production of urine, dark yellow to brown urine, and losing of pink cheeks and effect of eyes.

4. Listeria

Back in 1980’s, most problems were caused by the bacteria Listeria which are associated with cattle or sheep. Later, it got changed with outbreaks related to food occurred in many cities such as Nova Scotia, California, Texas, Massachusetts and many other cities. As it grows suitably in the environment and widespread distribution, the bacteria has grown ability to survive for longer time under unfavorable conditions and its ability to survive longer at colder temperatures in refrigerator. For that Listeria is now regarded as pivotal food borne pathogen responsible for severe illness.

Humana with weaker immunity system such as pregnant women’s or the older people are highly susceptible to Listeria. The most constant pathogenic species of Listeria genus is Listeria monocytogenes that causes Listeriosis.

In humans, the bacteria is ingested into the body is marked by a flu like symptom or illness that could be mild or severe. If it is mild, they can go unnoticed where a carrier state can develop into the body.

Death is unusual in the case of healthy humans, although the mortality rate may range around 30 percent in the immune weakened or infants or very young babies.

As above said Listeria monocytogenes is a problem that require special attention as it can survive unfavorable conditions. The bacteria can grow in optimum pH of 5-9.5 in suitable growth medium. The bacteria has known to survive pH range of 5 environment of cottage cheese and ripening cheddar products. Listeria can tolerate salt concentrations ranging as high of 30.5 percent for 100 days with temperature of 39.2 °F. And if kept for 5 days it goes for temperature 98.5 °F.

The main drawback is the cold temperature in refrigerator does not stop the growth of Listeria. The bacteria can double itself in every 1.5 days in greater number. However, heat can resist the growth of Listeria, like heat above 170 degrees Fahrenheit will inactivate the organism

Listeria, post process contamination of the bacteria from environment can become difficult to control its contamination in many food products. As listeria growth is slow in refrigerator due to low temperature, the rotation or change of food products become even more important step of prevention.

Source of bacteria – Listeria can grow effectively in unpasteurized milk and dairy products like cheese prepared from unpasteurized milk such as feta cheese, camembert, queso fresco cheese. Some of the other source can be raw vegetables and fruits like sprouts, ready to eat packed meats and hot dogs, spreads, seafood.

Incubation period to grow Listeria is usually 1-4 weeks and can stay for as long as 70 days.

Duration for this illness can range from several days to weeks.

Symptoms can be severe Listeriosis that include spread of bacteria beyond gut. Also, listeria can cause diarrhea and mild fever likely to other pathogenic foodborne bacteria, however this type of infection is rarely diagnosed. They also include rigid neck, confusion, imbalance and convulsions along with fever and muscle cramps.

Adults above 65 or more year, pregnant women and their infants, and people with weak immune system should take proper care to prevent this illness.


  • Don’t eat raw milk and their processed products like cheese as they get contaminated at the time of making with Listeria.
  • Don’t keep the melon for long if you have cut it. Eat right away or keep it in refrigerator.
  • You should not eat hot dogs, meat spreads, milk made from unpasteurized milk etc. They carry listeria contamination and should be avoided to stay healthy.
  • Always wash hands before or during cooking as it is the main stage where contamination occur. Always keep the food covered in the refrigerator for freshness and mixing of odor of different food products.

5. Clostridium perfringens

They are found in dust, soil, and gastrointestinal tracts of humans and animals. When food products which contains C.perfringes is consumed, the bacteria release a toxin in the intestine that causes illness. The bacteria exist as heat resistant spore bacteria so that it can survive the cooking temperature and survive to grow to produce large number of colonies if the cooked food kept in 40°F to 140°F temperature for longer time period. The main source of this bacteria is in meat, chicken dishes, sauces, spreads and can curries. Cooked food should be served hot to prevent to contact with bacteria. When refrigerate large quantity dishes, divide them into smaller portions to speed up the cooling process.

6. Vibrio parahaemolyticus

The bacteria is commonly found on seafood and needs salt environment of ocean to grow. The bacteria show the sensitivity to cold and heat stress. The proper storage required for seafood below the temperature of 40°F and subsequent cooking temperature should be above 140°F. This will abolish the growth of V.parahaemolyticus present on seafood.

Food poisoning due to the infection of this bacteria results by the improper or under cooking of food and contamination of cooked food by the contact of raw products followed by improper temperature of storage. It is main problem in Japan where most of the seafood are eaten raw.

V.vulnificus is other member of the genus Vibrio that is found in marine environment. It is rising pathogen but can be controlled and managed with proper cooking and refrigeration of food.

Proper precautions can save you from contamination of any of the stated food poisoning bacteria. Keep food in refrigeration for longer preservation and away from contamination.

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