Symptoms
According to the World Health Organization, there are 1.4 million salmonella infections in the United States each year. Of these, only 40,000 are reported to the U.S. Centers for Disease Control & Prevention (CDC) as "culture-proven." That means the rest are diagnosed solely on the basis of history.
When a doctor or other health professional takes a health history, he usually begins with symptoms. Salmonella causes mild, self-limited gastroenteritis. Symptoms including fever, abdominal pain and diarrhea, usually develop within 12 to 72 hours of infection and resolve within 4 to 7 days. Other symptoms such as bloody diarrhea could mean the problem is caused by something other than salmonella.
The course of symptoms is also used to determine the diagnosis. In healthy adults, viral gastroenteritis usually resolves within 24 to 72 hours, much faster than salmonella. Meanwhile, gastroenteritis due to medical problems such as inflammatory bowel disease usually takes longer than salmonella to resolve and may not go away at all without treatment.
Exposure
In order to diagnose salmonella on the basis of history, the physician will look to corroborate the symptoms with possible exposures to salmonella bacteria. It's helpful if the patient's family members or other associates also developed symptoms after consuming the same food or beverage. Sometimes patients will describe eating a food that tasted or smelled "off" or they will describe a risk factor for salmonella infection, such as eating undercooked eggs. In other cases, symptoms can be corroborated by checking the U.S. Food and Drug Administration food recall list or visiting the CDC web site for information about recent outbreaks.
Stool Cultures
Stool cultures are considered the gold standard for diagnosing salmonella infections. A patient can provide a sample taken at the doctor's office or hospital, or he can bring one from home, provided that a clean container is used. Since salmonella is rarely associated with serious illness and usually resolves without treatment, stool cultures might not be ordered.
