Salmonella is a very common organism, being naturally present in healthy birds and mammals. The proximity of animals to growing produce leads to the potential for contaminated water supplies used in irrigation, produce washing. There is also the possibility for wash-off during heavy rains. Salmonella can survive in the soil for months. Cross contamination in food processing operations is also a leading cause of Salmonellosis outbreaks.
The organism is one of the top causes of food borne illness and the second most common intestinal infection in the United States. A 2011 report by the Centers for Disease Control and Prevention, estimates that over 1 million people in the U.S. contract Salmonella each year, and that an average of 20,000 hospitalizations and almost 400 deaths occur from Salmonella poisoning.
Anyone of any age may become infected with Salmonella. Particularly vulnerable are people with weak immune systems, such as the very young and the elderly, people with HIV or chronic illnesses, and people on some medications; for example, chemotherapy for cancer or the immunosuppressive drugs used to treat some types of arthritis.
Salmonella is a motile, non-spore forming, Gram negative, rod-shaped bacterium in the family Enterobacteriaceae and the tribe Salmonellae. Non-motile variants include S. Gallinarum and S. Pullorum. The genus Salmonella is divided into two species that can cause illness in humans: S. enterica and, S. bongori.
Salmonella enterica, which is of the greatest public health concern, is comprised of six subspecies and these are further subdivided into serotypes. As of 2007, 2,579 different serotypes had been discovered.
Source: FDA Bad Bug Book
Salmonella illnesses fall into two groups; Nontyphoidal Salmonellosis and Typhoid Fever.
The tables below give an overview of the organism, its impact on humans, along with sources and the controls usually employed to prevent illness. This information may be used in growing and food processing operations as part of a HACCP food safety plan or preventive controls food safety plan.
|General:||The symptoms of nontyphoidal salmonellosis are normally very unpleasant, but is usually self-limiting in healthy people who have a good immune system. It may be life threatening however, particularly in the very young, the very old and those with compromised immune systems such as those with cancer, HIV, other auto-immune and underlying health conditions.|
|Caused by:||serotypes other than S. Typhi and S. Paratyphi A.|
|Mortality:||Usually <1%; however,
S. Enteritidis: 3.6% mortality rate in the elderly.
|Onset:||6 to 72 hours after exposure.|
|Infective dose:||As low as one cell, depending on age and health of host and strain differences among members of the genus.|
|Symptoms:||Nausea, vomiting, abdominal cramps, diarrhoea, fever, headache.|
|Duration:||Symptoms generally last 4 to 7 days, with acute symptoms usually lasting 1 to 2 days or longer, depending on host factors, the dose ingested, and strain characteristics.|
|Complications:||(1) Dehydration and electrolyte imbalance may occur as a result of diarrhea and vomiting. This can lead to death in the very young, the elderly, and the immunocompromised, if not treated promptly.
(2) In 2% of cases, reactive arthritis (i.e., arthritis from an immune reaction to the infection – an autoimmune response – rather than directly from the infection itself) may follow 3 to 4 weeks after the onset of acute symptoms. Indications of reactive arthritis may include, joint inflammation, urethritis, uveitis, and/or conjunctivitis.
(3) Nontyphoidal Salmonella can sometimes escape from the gastrointestinal tract into the body and cause blood poisoning (septicemia) or infect the blood, internal organs, and/or joints (bacteremia). S. Dublin is sometimes associated with this complication.
|Route of entry:||Oral (e.g., ingestion of contaminated food, fecal particles, or contaminated water).|
|Pathway:||Penetration and passage of Salmonella organisms from gut lumen into epithelium of small intestine, where inflammation occurs. There is evidence that enterotoxin may be produced, perhaps within enterocytes.|
|Implicated foods:||Poultry, raw eggs, meat, fish, contaminated / adulterated produce.|
|General:||Typhoid fever is more serious and has a higher mortality rate than nontyphoidal salmonellosis.|
|Caused by:||Serotypes S. Typhi and S. Paratyphi A, both of which are found only in
|Mortality:||Untreated, as high as 10%.|
|Onset:||Generally, 1 to 3 weeks, but may be as long as 2 months after exposure.|
|Infective dose:||Fewer than 1,000 cells.|
|Symptoms:||High fever, from 103° to 104°F (39.4°C to 40°C); lethargy; gastrointestinal symptoms, including abdominal pains and diarrhoea or constipation; headache; achiness; loss of appetite. A rash of flat, rose-colored spots sometimes occurs.|
|Duration:||Generally, 2 to 4 weeks.|
|Complications:||Septicemia, with colonization of other tissues and organs; e.g., may lead to endocarditis. Septic arthritis may occur, in which the infection directly affects the joints and may be difficult to treat. Chronic infection of the gallbladder may occur, which may cause the infected person to become a carrier.|
|Route of entry:||Oral (e.g., ingestion of contaminated food, fecal particles, or contaminated water).|
|Pathway:||Penetration and passage of typhoid Salmonella organisms from gut lumen into epithelium of small intestine and into the bloodstream (i.e., septicemia), which may carry the organisms to other sites in the body, where inflammation occurs. There is evidence that enterotoxin may be produced, perhaps within enterocytes.|
It is clear from the many documented cases that Salmonella represents a major health problem to humans and causes untold suffering and death. This is in addition to the cost to industry, health services and the damage caused to high profile food company brands, many of whom struggle to recover from outbreaks. The advent of social media means that food companies have nowhere to hide and are easily exposed for the lack of controls they have in place. This means that food businesses must be extra vigilant with respect to the preventive controls in place in their food processing and storage operations. Increased oversight over the preventive controls in their supply chains is critical to prevent illness and to operate a profitable and sustainable food business.
Sources of Salmonella:
Salmonella is common in nature and an understanding of its sources is vital to implementing controls to prevent its spread and contamination or adulteration of food and water. Salmonella lives in the intestinal tracts of vertebrates including livestock, wildlife, domestic pets and humans. It also lives in environments such as pond-water sediment. In animals, it is spread through the fecal-oral route and through contact with contaminated water. (Certain protozoa may act as a reservoir for the organism).
It may contaminate meat, farm-irrigation water (thus contaminating produce in the field), soil and insects, factory equipment, hands, and kitchen surfaces and utensils. Since S. Typhi and S. Paratyphi A are found only in human hosts, the usual sources of these organisms in the environment are drinking and/or irrigation water contaminated by untreated sewage. It is therefore highly recommended that only potable water and cooked vegetables be consumed in areas where these organisms are endemic. Various Salmonella species have long been isolated from the outside of egg shells but S. Enteritidis can be present inside the egg. This, and other information, strongly suggest vertical transmission; i.e., deposition of the organism on the albumen (egg white) side of the yolk-sack membrane (vitelline membrane) by an infected hen, prior to shell formation. Outbreaks also have been linked to the handling of certain animals sometimes kept as pets, such as turtles, frogs, and chicks.
Salmonella in Food
Although Salmonella is traditionally associated with animal products, fresh produce has also been the source of major outbreaks, particularly recently. The organism also survives well on low-moisture foods, such as spices, which have been the vehicles for large outbreaks.
Foods linked to Salmonella:
Meats, poultry, eggs, milk and dairy products, fish, shrimp, spices, yeast, coconut, sauces, freshly prepared salad dressings made with unpasteurized eggs, cake mixes, cream-filled desserts and toppings that contain raw egg, dried gelatin, peanut butter, cocoa, produce (fruits and vegetables, such as tomatoes, peppers, and cantaloupes) and chocolate.
The reason that so many foods can become contaminated or adulterated with Salmonella is down to the very low infective dose (as low as one viable bacterial cell) and the wide range of conditions that Salmonella species can survive in. This means that the two main controls are prevention of cross contamination in the first place and proper cooking to destroy any viable cells in contaminated food. This low infective dose also makes Salmonella unusual (but not unique), but means that it does not need to grow to be dangerous, its presence is enough, that is why prevention of cross contamination onto ready to eat foods (RTE) is so important.
Cross contamination occurs when Salmonella is spread from a contaminated source – a contaminated food or an infected food handler or animal – to other foods or objects in the environment. An example of how this may occur is when potentially contaminated raw meats, poultry, seafood, produce, or eggs are not kept separate from each other during preparation or cooking, or when a food handler does not adequately clean utensils, surfaces, equipment, and hands after they have come into contact with these products. The contamination can spread to factory and equipment surfaces, as well as kitchen surfaces and utensils. Cross contamination may occur at any point in the food process. Cross contamination may also occur from handling pets or wildlife, such as turtles or frogs (or their water, soil, or food and water bowls), then handling food, food-preparation utensils, or other objects in the environment. Limiting Conditions (including kill temperatures):
The following table gives the conditions that can be used to limit the growth of Salmonella.
|Growth temperature||41oF / 5.2oC||96-109oF / (35-43oC)||115oF / 46.2oC|
|Water activity (aw)||9.94||0.99||>0.99|
|Max % water phase salt||N/A||N/A||8|
Kill temperatures for Salmonella include heating to:
- 131oF (55oC) for one hour
- 140 oF (60oC) degrees for a half-hour
- 167 oF (75oC) for 10 minutes
When it comes to killing microorganisms, both temperature and time determine the effectiveness of the result. In addition, the kill temperatures must be measured in the center of the food product to ensure the minimum core temperature required for organism death is achieved.
Preventive Plan Assessment:
When reviewing a preventive plan for any of the affected foods above (or any food that could come into contact with Salmonella contaminated sources), the key controls you must look for may include the following:
- Water Sources – Prevention of use of sewage contaminated water sources for irrigation, washing or processing, only potable water sources are to be used.
- Other Food Sources – Prevention of cross contamination from potential Salmonella sources (such as water, raw meat, raw poultry, raw eggs, raw fish and other animal sources) to food, ingredients and food processing surfaces or equipment.
- Food handlers – Exclusion of food handlers (including farm workers and field workers) who have recently been sick and may be carriers of Salmonella. Proper hand washing and hygiene facilities and procedures.
- Medical Testing – Medical testing of food handlers, who have been sick, before allowing return to work to prevent human cross contamination.
- Kill Temperatures – For cooked and ready to eat foods that have a thermal processing step, ensure that adequate temperature controls are in place and all kill temperatures are being achieved.
- Preventive Controls – For ready to eat foods that do not have a thermal processing step, ensure that rigorous prevention controls are in place and that regular Salmonella testing takes place.
- Packaging Integrity – For raw foods, intended to be cooked by the consumer or further processed, ensure that packaging is secure and leak proof so that other foods are not contaminated.
- Cooking Instructions – For raw foods, intended to be cooked by the consumer or further processed, ensure that clear cooking instructions are given to consumers, including, in the case of meats, the instruction not to wash the meat before cooking (this spreads Bacteria in their kitchen / processing area). Also, ensure that the correct cooking times and temperatures are clearly displayed on the product label cooking instructions.
We hope this Salmonella Prevention Fact Sheet has been informative and can be used to help you assess the safety of foods that you process or purchase from. The team at 3iVerify are highly experienced and qualified food safety consultants. Our 3iVerify solution can help take the time, hassle and risk out of risk assessing your suppliers and reduce the risk of your company falling foul of Salmonella and other food safety risks. If you would like to know more about how 3iVerify can help you reduce risks, save time and prevent food borne illness and brand damage, or you have any questions regarding the above, please feel free to contact us below.