Salmonellosis

Salmonellosis
Electron micrograph showing Salmonella typhimurium (red) invading cultured human cells
Classification and external resources
Specialty	Infectious disease
ICD-10	A02.0
ICD-9-CM	003.0
DiseasesDB	11765
MedlinePlus	000294
Patient UK	Salmonellosis

Salmonellosis is an infection caused by Salmonella bacteria. Most people infected with Salmonella develop diarrhea, fever, vomiting, and abdominal cramps 12 to 72 hours after infection. In most cases, the illness lasts four to seven days, and most people recover without treatment. In some cases, the diarrhea may be so severe that the patient becomes dangerously dehydrated and must be hospitalized.

Intravenous fluids may be used to treat dehydration. Medications may be used to provide symptomatic relief, such as fever reduction. In severe cases, the Salmonella infection may spread from the intestines to the blood stream, and then to other body sites; this is known as typhoid fever and is treated with antibiotics.

The elderly, infants, and those with impaired immune systems are more likely to develop severe illness. Some people afflicted with salmonellosis later experience reactive arthritis, which can have long-lasting, disabling effects. There are just two species of Salmonella, Salmonella bongori and Salmonella enterica. The latter is divided in 6 subspecies: enterica, salamae, arizonae, diazonae, houtenase and indica. These subspecies are further divided into numerous serovars. Because the serovars only differ in serotypes, and therefore in infection potential, the serovars are not italicised and are written with a capital letter as they still belong to the same subspecies.

The species Salmonella enterica subsp. enterica contains over 60% of the total number of serovars and 99% of the serovars that are capable of infecting cold and warm blooded animals as well as humans. Infections are usually contracted from sources such as:

• Poultry, pork, beef and fish (seafood), if the meat is prepared incorrectly or is infected with the bacteria after preparation
• Infected eggs, egg products, and milk when not prepared, handled, or refrigerated properly
• Tainted fruits and vegetables

Reptiles such as red-eared slider turtles and green iguanas may carry Salmonella bongori (which inhabits cold-blooded animals) in their intestines which can cause intestinal infections. The most severe human Salmonella infection is caused by S. enterica subsp. enterica ser. Typhi which leads to typhoid fever; an infection that often proves fatal if not treated with the appropriate antibiotics. This serovar is restricted to humans and is usually contracted through direct contact with the fecal matter of an infected person. Typhoid fever is endemic in the developing world, where unsanitary conditions are more likely to prevail, and which can affect as many as 21.5 million people each year. Recorded cases of typhoid fever in the developed world are mostly related to recent travel in areas where Salmonella Typhi is endemic.

Signs and symptoms

Enteritis

After a short incubation period of a few hours to one day, the bacteria multiply in the intestinal lumen, causing an intestinal inflammation. Most people with salmonellosis develop diarrhea, fever, vomiting, and abdominal cramps 12 to 72 hours after infection. Diarrhea is often mucopurulent (containing mucus or pus) and bloody. In most cases, the illness lasts four to seven days, and most people recover without treatment. In some cases, though, the diarrhea may be so severe that the patient becomes dangerously dehydrated and must be taken to a hospital. At the hospital, the patient may receive intravenous fluids to treat the dehydration, and may be given medications to provide symptomatic relief, such as fever reduction. In severe cases, the Salmonella infection may spread from the intestines to the blood stream, and then to other body sites, and can cause death, unless the person is treated promptly with antibiotics.

In otherwise healthy adults, the symptoms can be mild. Normally, no sepsis occurs, but it can occur exceptionally as a complication in the immunocompromised. However, in people at risk such as infants, small children, the elderly, Salmonella infections can become very serious, leading to complications. In infants, dehydration can cause a state of severe toxicity. Extraintestinal localizations are possible, especially Salmonella meningitis in children, osteitis, etc. Children with sickle cell anemia who are infected with Salmonella may develop osteomyelitis. Treatment of osteomyelitis, in this case, will be to use fluoroquinolones (ciprofloxacin, levofloxacin, etc. and nalidixic acid).

Those whose only symptom is diarrhea usually completely recover, but it can be several months until their bowel habits are normal. A small number of people afflicted with salmonellosis experience reactive arthritis, which can last months or years and can lead to chronic arthritis. In sickle-cell anemia, osteomyelitis due to Salmonella infection is much more common than in the general population. Though Salmonella infection is frequently the cause of osteomyelitis in sickle-cell anemia patients, it is not the most common cause; the most common cause remains Staphylococcus infection.

Typhoid fever

See also: Typhoid fever and Paratyphoid fever

Typhoid fever occurs when Salmonella bacteria enter the lymphatic system and cause a systemic form of salmonellosis. Endotoxins first act on the vascular and nervous apparatus, resulting in increased permeability and decreased tone of the vessels, upset thermal regulation, vomiting and diarrhea. In severe forms of the disease, enough liquid and electrolytes are lost to upset the water-salt metabolism, decrease the circulating blood volume and arterial pressure, and cause hypovolemic shock. Septic shock may also develop. Shock of mixed character (with signs of both hypovolemic and septic shock) are more common in severe salmonellosis. Oliguria and azotemia develop in severe cases as a result of renal involvement due to hypoxia and toxemia.

Causes

An infographic illustrating how Salmonella spreads from the farm

• Contaminated food, often having no unusual look or smell;
• Poor kitchen hygiene, especially problematic in institutional kitchens and restaurants because this can lead to a significant outbreak;
• Excretions from either sick or infected but apparently clinically healthy people and animals (especially dangerous are caregivers and animals);
• Polluted surface water and standing water (such as in shower hoses or unused water dispensers);
• Unhygienically thawed fowl (the meltwater contains many bacteria);
• An association with reptiles (pet tortoises, snakes, iguanas, and aquatic turtles) is well described.
• Amphibians such as frogs may also carry the disease.

Salmonella bacteria can survive for some time without a host; thus, they are frequently found in polluted water, with contamination from the excrement of carrier animals being particularly important.

The European Food Safety Authority (EFSA) highly recommends that when handling raw turkey meat, consumers and people involved in the food supply chain should pay attention to personal and food hygiene.

An estimated 142,000 Americans are infected each year with Salmonella Enteritidis from chicken eggs, and about 30 die. The shell of the egg may be contaminated with Salmonella by feces or environment, or its interior (yolk) may be contaminated by penetration of the bacteria through the porous shell or from a hen whose infected ovaries contaminate the egg during egg formation.

Nevertheless, such interior egg yolk contamination is theoretically unlikely. Even under natural conditions, the rate of infection was very small (0.6% in a study of naturally contaminated eggs and 3.0% among artificially and heavily infected hens).

Prevention

See also: Critical control point

The FDA has published guidelines to help reduce the chance of food-borne salmonellosis. Food must be cooked to 68–72 °C (145–160 °F), and liquids such as soups or gravies must be boiled. Freezing kills some Salmonella, but it is not sufficient to reliably reduce them below infectious levels. While Salmonella is usually heat-sensitive, it does acquire heat resistance in high-fat environments such as peanut butter.

Vaccine

Antibodies against Non-typhoidal Salmonella were first found in Malawi children in research published in 2008. The Malawian researchers have identified an antibody that protects children against bacterial infections of the blood caused by Non-typhoidal Salmonella. A study at Queen Elizabeth Hospital in Blantyre found that children up to two years old develop antibodies that aid in killing the bacteria. This could lead to a possible Salmonella vaccine.

A recent study has tested a vaccine on chickens which offered efficient protection against salmonellosis.

Treatment

Electrolytes may be replenished with oral rehydration supplements (typically containing salts sodium chloride and potassium chloride). Appropriate antibiotics, such as ceftriaxone, are given to kill the bacteria. Azithromycin has been suggested to be better at treating typhoid in resistant populations than both fluoroquinolone drugs and ceftriaxone. Antibiotic resistance rates are increasing throughout the world, so health care providers should check current recommendations before choosing an antibiotic.

Epidemiology

About 142,000 people in the United States are infected each year with Salmonella Enteritidis from chicken eggs, and about 30 die.

In 2010, an analysis of death certificates in the United States identified a total of 1,316 Salmonella-related deaths from 1990 to 2006. These were predominantly among older adults and those who were immunocompromised.

Before 2006

The U.S. Government reported as many as 20% of all chickens were contaminated with Salmonella in the late 1990s, and 16.3% were contaminated in 2005. In the mid- to late 20th century, Salmonella enterica serovar Enteritidis was a common contaminant of eggs. This is much less common now with the advent of hygiene measures in egg production, and the vaccination of laying hens to prevent Salmonella colonization. Various Salmonella serovars (strains) also cause severe diseases in animals.

2006

In June 2006, the BBC reported the Cadbury chocolate manufacturer withdrew a number of products contaminated with Salmonella, which had resulted in up to 56 cases of salmonellosis. The causes had been traced to a leaking pipe at a Cadbury plant in Herefordshire in January 2006, though the announcement was not made until June.

2007

In February 2007, the U.S. Food and Drug Administration (FDA) issued a warning to consumers not to eat certain jars of Peter Pan or Great Value peanut butter, due to risk of contamination with Salmonella Tennessee.[2]

In March 2007, around 150 people were diagnosed with salmonellosis after eating tainted food at a governor's reception in Krasnoyarsk, Russia. Over 1,500 people attended the ball on March 1, and fell ill as a consequence of ingesting salmonella-tainted sandwiches.

About 150 people were sickened by salmonella-tainted chocolate cake produced by a major bakery chain in Singapore, in December 2007.[3]

2008

Main article: 2008 United States salmonellosis outbreak

From April 10, 2008 to July 8, 2008, the rare Saintpaul serotype of S. enteritidis caused at least 1017 cases of salmonellosis food poisoning in 41 states throughout the United States, the District of Columbia, and Canada. As of July 2008, the U.S. FDA suspected the contaminated food product was a common ingredient in fresh salsa, such as raw tomato, fresh jalapeño pepper, fresh serrano pepper, and fresh cilantro. It is the largest reported salmonellosis outbreak in the United States since 1985. New Mexico and Texas have been proportionally the hardest hit by far, with 49.7 and 16.1 reported cases per million, respectively. The greatest number of reported cases have occurred in Texas (384), New Mexico (98), Illinois (100), and Arizona (49). At least 203 reported hospitalizations have been linked to the outbreak, it has caused at least one death, and it may have been a contributing factor in at least one additional death. The CDC maintains "it is likely many more illnesses have occurred than those reported." If applying a previous CDC-estimated ratio of unreported salmonellosis cases to reported cases (38.6:1), an estimated 40,273 illnesses occurred from this outbreak.

As of 18 July 2008, the FDA removed raw tomatoes and cilantro as potential carriers; however, fresh jalapeño and serrano peppers still remain.

In December 2008 and January 2009, several Midwestern states, including Ohio (officially confirmed by state authorities), reported an outbreak of salmonellosis from Salmonella typhimurium that had sickened at least 50 people, due to contaminated dairy products such as cheeses.

2009

Main article: Peanut Corporation of America

On January 17, 2009, the FDA announced they had traced the source of an outbreak of Salmonella typhimurium to a plant in Blakely, Georgia, owned by Peanut Corporation of America (PCA), and urged people to postpone eating commercially prepared or manufactured peanut butter-containing products and institutionally served peanut butter. Salmonella was reported to be found in 46 states in the United States in at least 3,862 peanut butter-based products, such as crackers, energy bars, and peanut butter cookies from at least 343 food companies. Dog treats were affected, as well. At least 691 people in more than 46 states became sick, and the Salmonella claimed at least 9 lives as of March 25.

Peanut butter and peanut paste manufactured by PCA were distributed to hundreds of firms for use as an ingredient in thousands of different products, such as cookies, crackers, cereal, candy and ice cream, all of which were recalled. Some products were also sold directly to consumers in retail outlets, such as dollar stores.

On March 14, 2009, expressing his own personal concern for the safety of his children who enjoy peanut butter, President Obama announced the establishment of the Food Safety Working Group, "an inter-agency effort to help overhaul the oversight system." The announcement came days after the FDA, also responding, released its first "guidance" on dealing with Salmonella contamination.

2012

See also: 2012 salmonella outbreak

An outbreak of salmonellosis caused by a rarer subspecies, Salmonella bareilly, was reported in multiple states mostly in the East, having yet caused no deaths, but many episodes of sickness and some hospitalizations have been linked to the consumption of raw scraped ground tuna product.

Since July 2012, an outbreak of salmonellosis occurred in Northern Europe caused by Salmonella thompson. The infections were linked to smoked salmon from the manufacterer Foppen, where the contamination had occurred. Most infections were reported in the Netherlands, over 1060 infections with this subspecies have been confirmed, as well as four mortalities.

A case of widespread infection was detected mid-2012 in seven EU countries. Over 400 people had been infected with Salmonella enterica serovar Stanley (S. Stanley) that usually appears in the regions of Southeast Asia. After several DNA analyses seemed to point to a specific Belgian strain, the "Joint ECDC/E FSA Rapid Risk Assessment" report detected turkey production as the source of infection.

History

Both salmonellosis and the Salmonella genus of microorganisms derive their names from a modern Latin coining after Daniel E. Salmon (1850–1914), an American veterinary surgeon. He had help from Theobald Smith, and together they found the bacterium in pigs.

Four-inch regulation

The "Four-inch regulation" or "Four-inch law" is a colloquial name for a regulation issued by the U.S. FDA in 1975, restricting the sale of turtles with a carapace length of less than four inches (10 cm).

The regulation was introduced, according to the FDA, "because of the public health impact of turtle-associated salmonellosis." There had been reported cases of young children placing small turtles in their mouths, which led to the size-based restriction.

See also

• 1984 Rajneeshee bioterror attack
• List of foodborne illness outbreaks

External links

• CDC website, Division of Bacterial and Mycotic Diseases, Disease Listing: Salmonellosis
• CFIA Website: Salmonellae
• Protective salmonella antibodies found in Malawi children, Sub-Saharan Africa gateway, Science and Development Network, [4]