Salmonella

Salmonella

Salmonella Outbreak Slideshow

Medical Author: Charles Davis, MD, PhD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

• What is Salmonella?
• Who discovered Salmonella?
• What are symptoms of Salmonella infection?
• How is Salmonella transmitted to humans?
• How do Salmonella spp cause disease in people?
• How do you diagnose Salmonella infections?
• How are Salmonella infections treated?
• How can Salmonella infections be prevented?
• Where can I find more information about Salmonella?
• Salmonella At A Glance
• Pictures of Salmonella Outbreak - Slideshow
• Patient Discussions: Salmonella - Describe Your Symptoms Experienced

What is Salmonella?

Salmonella (S.) is the genus name for a large number (over 2,500) of types of bacteria. Each type is distinctly identifiable by its specific protein coating. The types are otherwise closely related. Salmonella bacteria are rod-shaped, flagellated, Gram stain-negative, and are known to cause disease in humans, animals, and birds (especially poultry) worldwide.

The terminology that identifies the particular protein coats, or serovars, is not well settled, and what previously were thought to be various species of the genus Salmonella are now thought to be serovars of only two species by many researchers, S. enterica and S. bongori. However, these designations are not always accepted in the scientific literature and so common serovars that have been named in the past are still used (for example, S. typhi, S. typhimurium, S. enteritidis, S. cholerasuis, S. saintpaul). The serovars are identified by the Kauffman-White classification that uses two major types of antigens (somatic O and flagellar H) to distinguish the over 2,500 types of Salmonella bacteria. Sometimes laboratories or other reporting agencies identify isolates simply as Salmonella spp (species) and do not identify the serovars.

Who discovered Salmonella?

The bacteria were first isolated by Theobald Smith in 1885 from pigs. The genus name Salmonella was derived from the last name of D.E. Salmon, who was Smith's director.

What are symptoms of Salmonella infections?

Salmonellosis (gastroenteritis characterized by nausea, vomiting, and diarrhea) is the most common disease caused by the organisms. Abdominal cramping also may occur. Salmonellosis thus produces the symptoms that are commonly referred to as food poisoning. Although food poisoning is usually a mild disease, nausea, vomiting, and diarrhea can lead to dehydration and even death (about 500 per year in the U.S.). It is important to note that many other organisms (for example, viruses, E. coli, Shigella) and toxins (for example, botulism, mushroom toxin, pesticides) can produce food poisoning symptoms. However, over 1.4 million cases of salmonellosis occur per year in the U.S., and the rest of industrialized countries have similar high rates. Countries with poor sanitation have a much higher incidence of salmonellosis.

Typhoid fever occurs when some of the Salmonella organisms (often identified as S. typhi) are not killed by the normal human immune defenses (macrophage cells) after they enter the gastrointestinal tract. Salmonella then survive and grow in the human spleen, liver, and other organs and may reach the blood (bacteremia). Salmonella can be shed from the liver to the gallbladder, where they can continue to survive and be secreted into the patient's feces for up to a year. Symptoms include high fevers up to 104 F, sweating, inflammation of the stomach and intestines, and diarrhea. Symptoms usually resolve, but many patients become Salmonella carriers. Approximately half of patients develop slow heartbeat (bradycardia), and about 30% of patients get flat, slightly raised red or rose-colored spots on the chest and abdomen. Typhoid fever is also referred to as enteric fever.

Paratyphoid fever, also termed enteric fever, has symptoms like typhoid, but it's usually not as severe. Subtypes are A, B, and C and vary by having small changes in symptoms, such as more rose spots (A), in conjunction with herpes labialis and gastroenteritis (B), rarely, with septicemia and abscesses (C).

Salmonella - Describe Your Symptoms Experienced

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What were the symptoms and signs you experienced with Salmonella infection?

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