Salmonella Food Poisoning Health Article

Definition

Salmonella food poisoning is a bacterial infection that causes inflammation (swelling) of the lining of the stomach and intestines (gastroenteritis). The causative bacteria is called Salmonella. While domestic and wild animals, including poultry, pigs, cattle, and pets such as turtles, iguanas, chicks, dogs, and cats can transmit this illness, most people become infected by ingesting foods contaminated with significant amounts of the causative bacteria.

Description

Improperly handled or undercooked poultry and eggs are the foods which most frequently cause salmonella food poisoning. Chickens are a major carrier of salmonella bacteria, which accounts for its prominence in poultry products. However, identifying foods which may be contaminated with salmonella is particularly difficult because infected chickens typically show no signs or symptoms. Since infected chickens have no identifying characteristics, these chickens go on to lay eggs or to be used as meat.

At one time, it was thought that salmonella bacteria were only found in eggs which had cracked, thus allowing the bacteria to enter. Ultimately, it was learned that, because the egg shell has tiny pores, even uncracked eggs which sat for a time on a surface (nest) contaminated with salmonella could themselves become contaminated. It is known also that the bacteria can be passed from the infected female chicken directly into the substance of the egg before the shell has formed around it.

Anyone may contract salmonella food poisoning, but the disease is most serious in infants, the elderly, and individuals with weakened immune systems. In these individuals, the infection may spread from the intestines to the blood stream and then to other body sites, causing death unless the person is treated promptly with antibiotics. In addition, people who have had part or all of their stomach or their spleen removed or who have sickle cell anemia, cirrhosis of the liver, leukemia, lymphoma, malaria, louse-borne relapsing fever, or acquired Immunodeficiency syndrome (AIDS) are particularly susceptible to salmonella food poisoning.

Demographics

Although salmonella food poisoning occurs worldwide, it is most frequently reported in North America and Europe. Only a small proportion of infected people are tested and diagnosed, and as few as 1 percent of cases are actually reported. While the infection rate may seem relatively low, even an attack rate of less than 0.5 percent in such a large number of exposures results in many infected individuals. The poisoning typically occurs in small, localized outbreaks in the general population or in large outbreaks in hospitals, restaurants, or institutions for children or the elderly. In the United States, salmonella is responsible for about 15 percent of all cases of food poisoning.

Causes and symptoms

Salmonella food poisoning can occur when someone drinks unpasteurized milk or eats undercooked chicken or eggs, or salad dressings or desserts which contain raw eggs. Even if salmonella-containing foods such as chicken are thoroughly cooked, any food can become contaminated during preparation if conditions and equipment for food preparation are unsanitary.

Other foods can then be accidentally contaminated if they come into contact with infected surfaces. In addition, children have become ill after playing with turtles or iguanas and then eating without washing their hands. Because the bacteria are shed in the feces for weeks after infection with salmonella, poor hygiene can allow such a carrier to spread the infection to others.

Symptoms appear about one to two days after infection and include fever (in 50% of patients), nausea and vomiting, diarrhea, and abdominal cramps and pain. The diarrhea is usually very liquid and rarely contains mucus or blood. Diarrhea usually lasts for about four days. The illness usually ends in about five to seven days.

Serious complications are rare, occurring most often in individuals with other medical illnesses. Complications occur when the salmonella bacteria make their way into the bloodstream (bacteremia). Once in the bloodstream, the bacteria can enter any organ system throughout the body, causing disease. Other infections which can be caused by salmonella include:

• bone infections (osteomyelitis)
• joint infections (arthritis)
• infection of the sac containing the heart (pericarditis)
• infection of the tissues which cover the brain and spinal cord (meningitis)
• infection of the liver (hepatitis)
• lung infections (pneumonia)
• infection of aneurysms (aneurysms are abnormal outpouchings which occur in weak areas of the walls of blood vessels)
• infections in the center of already-existing tumors or cysts

Diagnosis

Under appropriate laboratory conditions, salmonella can be grown and then viewed under a microscope for identification. Early in the infection, the blood is far more likely to positively show a presence of the salmonella bacterium when a sample is grown on a nutrient substance (culture) for identification purposes. Eventually, however, positive cultures can be obtained from the stool and in some cases from a urine culture.