Salmonella is one of the most common enteric (intestinal) infections in the United States. Salmonellosis (the disease caused by Salmonella) is the second most common foodborne illness after Campylobacter infection. It is estimated that 1.4 million cases of salmonellosis occur each year in the U.S.; 95% of those cases are foodborne-related. Approximately 220 of each 1000 cases result in hospitalization and eight of every 1000 cases result in death. About 500 to 1,000 or 31% of all food-related deaths are caused by Salmonella infections each year. Salmonellosis is more common in the warmer months of the year.
Salmonella infection occurs when the bacteria are ingested, typically from food derived from infected food-animals, but it can also occur by ingesting the feces of an infected animal or person. Food sources include raw or undercooked eggs/egg products, raw milk or raw milk products, contaminated water, meat and meat products, and poultry. Raw fruits and vegetables contaminated during slicing have been implicated in several foodborne outbreaks.
Symptoms of Salmonella infection
The acute symptoms of Salmonella gastroenteritis include the sudden onset of nausea, abdominal cramping, and bloody diarrhea with mucous. Fever is almost always present. Vomiting is less common than diarrhea. Headaches, myalgias (muscle pain), and arthralgias (joint pain) are often reported as well. The onset of symptoms usually occurs within 6 to 72 hours after the ingestion of the bacteria. The infectious dose is small, probably from 15 to 20 cells.
Reiter’s Syndrome, which includes and is sometimes referred to, as reactive arthritis is an uncommon, but debilitating, result of a Salmonella infection. The symptoms of Reiter’s Syndrome usually occur between one and three weeks after the infection. Reiter’s Syndrome is a disorder that causes at least two of three seemingly unrelated symptoms: reactive arthritis, conjunctivitis (eye irritation), and urinary tract infection. The arthritis associated with Reiter’s Syndrome typically affects the knees, ankles, and feet, causing pain and swelling. Wrists, fingers and other joints can be affected, though with less frequency. With Reiter’s Syndrome, the affected person commonly develops inflammation where the tendon attaches to the bone, a condition called enthesopathy. Some people also develop heel spurs, bony growths in the heel that cause chronic or long-lasting foot pain. Arthritis from Reiter’s Syndrome can also affect the joints of the back and cause spondylitis, inflammation of the vertebrae in the spinal column. The duration of reactive arthritis symptoms can vary greatly. Most of the literature suggests that the majority of affected persons recover within a year. The condition, can, however, be permanent.
Detection and treatment of Salmonella Infection
Salmonella bacteria are discovered in stool cultures. Although blood cultures are rarely positive, bacteremia (bacteria in the blood stream) does occur in 5% of adults with Salmonella gastroenteritis and can result in spread to the heart (endocarditis), spleen, bone (osteomyelitis), and joints (Reiter’s Syndrome or reactive arthritis). However, blood cultures are often not performed and in most cases the blood stream is not infected. In the stool, the laboratory is challenged to pick out Salmonella from many other similar bacteria that are normally present. In addition, many persons submit cultures after they have started antibiotics, which may make it even more difficult for a microbiology lab to grow Salmonella. So, the diagnosis of salmonellosis may be problematic and many mild cases are culture negative.
Salmonella infections usually resolve in five to seven days, and many times require no treatment, unless the affected person becomes severely dehydrated or the infection spreads from the intestines. Persons with severe diarrhea may require rehydration, often with intravenous fluids. Treatment with antibiotics is not usually necessary, unless the infection spreads from the intestines, or otherwise persists, in which case the infection can be treated with ampicillin, gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin. Some Salmonella bacteria have become resistant to antibiotics, possibly as a result of the use of antibiotics to promote the growth of feed animals.
For those persons who develop Reiter’s Syndrome, symptomatic treatment with high doses of a nonsteroidal anti-inflammatory drug and steroid injections into affected joints can be helpful in reactive arthritis. For people with severe joint inflammation, injections of corticosteroids directly into the affected joint may reduce inflammation. A small percentage of patients with reactive arthritis have severe symptoms that cannot be controlled with these treatments, in which case medicine that suppresses the immune system, such as sulfasalazine or methotrexate, may be effective. Exercise, when introduced gradually, may help improve joint function. Topical corticosteroids can be applied directly on the skin lesions associated with reactive arthritis.
Preventing Salmonella Infection
To prevent salmonellosis, cook poultry, ground beef, and eggs thoroughly before eating. In order to insure that eggs do not contain viable Salmonella they must be cooked at least until the yoke is solid, and meat and poultry must reach 160∫F or greater throughout. Be particularly careful with foods prepared for infants, the elderly, and those with a compromised immune system.
Do not eat or drink foods containing raw eggs, such as homemade eggnog and hollandaise sauce. Avoid drinking raw (unpasteurized) milk or products made from raw milk.
Wash hands, kitchen work surfaces, and utensils with soap and water immediately after they have been in contact with foods of animal origin. Also, wash hands with soap after handling reptiles, amphibians or birds, or after contact with pet feces. Infants and immunocompromised persons should have no direct or indirect contact with such pets.
Salmonella Infection Complications
The following infections result in very few people, but the few who are diagnosed will suffer for the rest of their lives.
Irritable Bowel Syndrome (IBS)
A recently published study surveyed the extant scientific literature and noted that post-infectious irritable bowel syndrome (PI-IBS) is a common clinical phenomenon first described over five decades ago. The Walkerton Health Study further notes that:
Between 5% and 30% of patients who suffer an acute episode of infectious gastroenteritis develop chronic gastrointestinal symptoms despite clearance of the inciting pathogens.
In terms of its own data, the “study confirm[ed] a strong and significant relationship between acute enteric infection and subsequent IBS symptoms.” The WHS also identified risk factors for subsequent IBS, including: younger age; female sex; and four features of the acute enteric illness—diarrhea for > 7days, presence of blood in stools, abdominal cramps, and weight loss of at least ten pounds.
Irritable bowel syndrome (IBS) is a chronic disorder characterized by alternating bouts of constipation and diarrhea, both of which are generally accompanied by abdominal cramping and pain. In one recent study, over one-third of IBS sufferers had had IBS for more than ten years, with their symptoms remaining fairly constant over time. IBS sufferers typically experienced symptoms for an average of 8.1 days per month.
As would be expected from a chronic disorder, IBS sufferers required more time off work, spent more days in bed, and more often cut down on usual activities, when compared with non-IBS sufferers. And even when able to work, a significant majority (67%), felt less productive at work because of their symptoms. IBS symptoms also have a significantly deleterious impact on social well-being and daily social activities, such as undertaking a long drive, going to a restaurant, or taking a vacation. Finally, while a patient’s psychological state may influence the way in which he or she copes with illness, and responds to treatment, there is no evidence that supports the theory that psychological disturbances in facts cause IBS or its symptoms.
Several bacteria, including Salmonella, induce septic arthritis. The resulting joint pain and inflammation can resolve completely over time or permanent joint damage can occur. In a small number of persons, the joint inflammation is accompanied by conjunctivitis and uveitis, (inflammation of the eyes), and cystitis (painful urination). This triad of symptoms is called Reiter’s Syndrome. Reiter’s Syndrome is a special form of reactive arthritis, autoimmune disorder triggered by the Salmonella infection. It occurs in persons with a genetic predisposition and can last for a year or more. Antibiotic treatment does not make a difference in whether or not the person later develops arthritis.
The term reactive arthritis refers to an inflammation of one or more joints, following an infection localized at another site distant from the affected joints. The predominant site of the infection is the gastrointestinal tract. During outbreaks of Salmonella infections, reactive arthritis incidences from 1% to 15% have been reported.
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