Information for Healthcare Professionals and Laboratories

Salmonella was discovered more than a century ago. Salmonellosis, the illness caused by Salmonella, primarily results in a mild to severe diarrheal illness, known as acute gastroenteritis.

Symptoms

Symptoms of acute gastroenteritis due to infection with Salmonella can include⁹:

• Sudden onset of diarrhea (which may be bloody)
• Abdominal cramps
• Fever (almost always present)
• Nausea, vomiting, and headache may occur, though less frequent

Diarrhea may last for several days and lead to potentially severe dehydration, especially in infants and children under 2 years old and in adults over 65 years old. Even after clinical symptoms are no longer obvious, Salmonella bacteria may be found in the stool for several weeks.

Most people with diarrhea due to a Salmonella infection recover completely, although it may be several months before their bowel habits are entirely normal.

Sometimes, Salmonella infection can spread to urine, blood, bones, joints, the brain, or the nervous system, causing symptoms related to that body part or system. Some of these extra-intestinal infections can have long-term effects, depending on which part of the body is infected.

Invasive Salmonella Infections

When Salmonella infections become invasive, they can affect the bloodstream, bone, joint, brain, or nervous system, or other internal organs.

Invasive Salmonella infections:

• Can be severe and potentially life-threatening.
• Occur in about 8 percent of persons with laboratory-confirmed Salmonella infection.¹⁰
• May occur as:
  • Bacteremia (infection of the blood)
  • Meningitis (infection of the membranes lining the brain and spinal cord)
  • Osteomyelitis (infection of the bone)
  • Septic arthritis (infection of a joint).
• Are rarely fatal, but most commonly occur in people who are very young or old or have a weakened immune system.

How is Salmonella infection treated?

Giving fluids is very important. Oral fluids are usually sufficient, but people with severe diarrhea may require intravenous (IV) fluids. Most people do not require antibiotics.

• See the 2017 Infectious Diseases Society of America Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea >

Should Salmonella infections be treated with antibiotics?

Antibiotics are NOT recommended for treating most patients with Salmonella infection.

Antibiotics are recommended for

• Patients with HIV infection.
• Other immunocompromised patients (e.g., organ transplant recipients; those receiving corticosteroids or other immunosuppressive agents;  those with cancer or lymphoproliferative disease with current or recent chemotherapy; and those with sickle cell disease, hemoglobinopathies, or disorders of the reticuloendothelial system, including cirrhosis).
• Patients older than age 50 with cardiac, valvular, or endovascular abnormalities, or substantial joint disease.
• People who have severe illness, such as severe diarrhea (nine to ten stools per day), high or persistent fever, or a condition requiring hospitalization.
• Adults age 65 or older.

In healthy people with Salmonella infection, antibiotics generally do not shorten the duration of illness, diarrhea, or fever. The main risks of treatment include adverse effects of the antibiotic, the possibility of prolonged asymptomatic Salmonella carriage, and disturbance of the microbiome. Unnecessary antibiotic use also contributes to antibiotic resistance.

What should I know about treating patients with resistant Salmonella infections?

If Salmonella bacteria are resistant, first-choice antibiotics recommended to treat these infections might not work. Healthcare providers might need to prescribe second- or third-choice drugs, but these might be less effective, administered through an IV instead of orally, more toxic, and more expensive. Recommended antibiotics for severe infections include fluoroquinolones, azithromycin, and third generation cephalosporins.

How does CDC track resistant Salmonella infections?

CDC tracks these infections through the National Antimicrobial Resistance Monitoring System (NARMS). The NARMS program at CDC helps protect public health by providing information about emerging bacterial resistance, the ways in which resistance is spread, and how resistant infections differ from susceptible infections.

Learn more about resistant Salmonella with these resources from NARMS.

• NARMS Annual Human Isolates Reports
• NARMS Now: Interactive graphics displaying antibiotic resistance data for Salmonella
• NARMS Publications

The genus Salmonella is a member of the family Enterobacteriaceae. Like other Enterobacteriaceae, Salmonellae are Gram-negative, rod-shaped bacilli. The genus Salmonella can be divided into two species (S. enterica and S. bongori), based on their phenotypic profile. S. enterica can be further divided into six subspecies using their phenotypic profile.

The most common serotypes of Salmonella that cause human infection are Enteritidis, Typhimurium, Newport, and Javiana. These Salmonella serotypes account for about half of culture-confirmed Salmonella isolates reported by public health laboratories¹².

Typhoidal and Nontyphoidal Salmonella

Salmonella bacteria are classified as either “typhoidal” or “nontyphoidal,” based on their serotype.

• Typhoidal Salmonella refers to the specific Salmonella serotypes which cause typhoid fever or paratyphoid fever, including Typhi, Paratyphi A, Paratyphi B (see note below), and Paratyphi C.
  • Serotype Paratyphi B is tartrate-negative (unable to ferment tartrate) and causes typhoidal disease. Serotype Paratyphi B var. L(+)tartrate+  is tartrate-positive (able to ferment tartrate) and causes nontyphoidal disease.
• Nontyphoidal Salmonella refers to all other Salmonella serotypes¹³.