Salmonellosis is an infection caused by Salmonella bacteria. It is a zoonotic disease i.e an infection that can be transmitted from animal to man and vice-versa. 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.
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 refrigeratedproperly.
Tainted fruits and vegetables
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
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.
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.
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 andanimals (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).
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. Control of Salmonella in poultry is a public health concern as Salmonella are a leading cause of human food poisoning. Poultry is not the only possible source of salmonellosis, but it is known to be a major global reservoir of Salmonellas.
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.
Compiled by Dr Belleh Efie
Vanguard Pharmacy Limited