1. Salmonella Outbreak Pictures Slideshow
2. Summer Food Safety Quiz: Test Your Food Safety IQ
3. Food Poisoning Slideshow Pictures

Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Salmonella poisoning facts
• What is Salmonella?
• What are Salmonella poisoning symptoms?
• How is Salmonella transmitted to humans?
• What are the risk factors for Salmonella infections?
• What are the unique situations that allow Salmonella to contaminate eggs?
• How do Salmonella spp. cause disease in people?
• How are Salmonella infections diagnosed?
• What is the treatment for Salmonella poisoning?
• What are the prognosis (outcome) and complications for Salmonella infections?
• How can Salmonella infection be prevented?
• Where can I find more information about Salmonella?
• Salmonella Outbreak - Slideshow
• Take the Quiz: Summer Food Safety
• Pictures of Food Poisoning - Slideshow
• Summer Food Safety FAQs
• Patient Comments: Salmonella - Treatments
• Patient Comments: Salmonella - Symptoms
• Salmonella Index

Usually, Salmonella spp. are ingested. It is commonly accepted that at between 1 million to 1 billion bacteria are needed to cause infection although some investigators suggest some people may be infected by far fewer bacteria. Nevertheless, most data suggest food, water, or other sources of contamination contain large amounts of bacteria. Although human stomach acid can reduce and sometimes eliminate Salmonella spp., occasionally some bacteria get through to the intestine and then attach and penetrate the cells. Toxins produced by the bacteria (enterotoxin and cytotoxin) can damage and kill the cells that line the intestines, which results in intestinal fluid loss (diarrhea).

Some Salmonella can survive in cells of the immune system and can reach the bloodstream, causing blood infection (bacteremia). Other Salmonella spp. can enter the gallbladder, leaving the affected patient a chronic carrier of the organisms. Salmonella can then be shed with the bile from the gallbladder into the feces and then may infect other people.

Feces of patients that have symptoms of food poisoning or typhoid fever are cultured for Salmonella. Often, the preliminary diagnosis is first suggested by recognition of an outbreak (multiple patients having symptoms of a disease all at about the same time and often from the same food or water source). Again, many organisms and toxins can cause food poisoning, so it is sometimes difficult to determine the outbreak's cause. Usually, the laboratory needs to be notified that S. spp. is suspected as the cause so they will choose the correct testing media (selective agar media such as SS agar plates) to distinguish Salmonella from other potential bacterial pathogens such as E. coli, Shigella strains, Campylobacter, Staphylococcus food poisoning, or from toxins like botulism or pesticides. The majority of Salmonella isolates come from the feces of the infected person. Occasionally, Salmonella can be cultured from blood samples. Serovars are identified by serotyping (detecting bacterial proteins by using specific immunological tests). Definitive diagnosis usually requires that the bacteria be isolated and identified by these techniques. PCR tests also have been used to distinguish between bacterial strains.