6333 – Nontyphoid salmonella infections

DBQ: Link to Index of DBQ/Exams by Disability for DC 6333

Definition

Nontyphoid Salmonella (NTS) infections are a group of illnesses caused by bacteria from the Salmonella genus, excluding those that cause typhoid fever (like Salmonella Typhi). These infections typically result in gastroenteritis, characterized by diarrhea, fever, and abdominal cramps. However, they can also lead to more severe, invasive infections with symptoms like bacteremia (bacteria in the blood) and focal infections in other organs. 

Etiology

Nontyphoid Salmonella infections are caused by various strains of the Salmonella enterica bacteria, with the most common being S. enterica subspecies enterica serotypes such as Enteritidis, Typhimurium, Newport, Heidelberg, and Javiana. 

Primary causes

• Ingestion of contaminated food or water: This is the most frequent route of infection.
  • Commonly contaminated foods: These include raw or undercooked meat (especially poultry and ground beef), poultry, eggs (even those with intact shells), egg products, unpasteurized milk, and some produce (fruits and vegetables), according to the Mayo Clinic and CDC.
  • Cross-contamination: Bacteria can spread from raw, contaminated foods to other foods if they are not kept separate, and through unwashed hands, chopping boards, and knives.
  • Contaminated water: Drinking water that has not been made safe, or using contaminated water for irrigation or cleaning produce, can lead to infection.
• Contact with infected animals: Animals and pets, especially reptiles and birds, can carry Salmonella bacteria in their feces and on their skin, fur, or feathers.
• Person-to-person transmission: Although less frequent, Salmonella can spread from a person with diarrhea to another person through inadequate handwashing, according to the CDC. 

Signs & Symptoms

Signs and symptoms of nontyphoid Salmonella infection (salmonellosis) can vary in severity but often include: 

Gastrointestinal symptoms

• Diarrhea: Often sudden onset, which may be watery, loose, bloody, or mucoid.
• Abdominal cramps or tenderness.
• Fever: Usually present.
• Nausea, vomiting, and headache: These may also occur, but are less frequent than the other symptoms. 

Less common but potentially serious complications

• Extra-intestinal infection: Salmonella can sometimes spread beyond the intestines to other parts of the body, including the urinary system, bloodstream (bacteremia), brain and spinal cord (meningitis), heart lining or valves (endocarditis), bones or bone marrow (osteomyelitis), or blood vessels.
• Reactive arthritis: Some individuals may develop joint pain, eye irritation, and painful urination, a condition known as reactive arthritis (or Reiter's syndrome), which can last for months or years. 

Dehydration

Severe diarrhea and vomiting can lead to dehydration, especially in infants, young children, older adults, and those with weakened immune systems. Watch for signs like: 

• Urinating less than usual or dark-colored urine
• Dry mouth and tongue
• Sunken eyes
• No tears when crying (in infants)
• Increased tiredness, irritability, or confusion 

Tests

Tests for nontyphoidal Salmonella infections primarily involve detecting the bacteria in a clinical sample or identifying antibodies produced in response to the infection. 

Here's a summary of the common tests:

1. Culture-based tests

• Stool Culture: This is the most common method for diagnosing Salmonella gastroenteritis (infection of the digestive tract). According to Marler Clark, a sample is placed in nutrient broth or on agar and incubated for up to 2-3 days, after which a microbiologist can identify the bacteria.
• Blood Culture: Used to detect bacteremia (bacteria in the bloodstream) or invasive infections. This is particularly important for patients at risk of severe illness or who show signs of disseminated infection.
• Other Cultures: In specific cases, such as focal infections (infections in specific body parts), urine, bile, cerebrospinal fluid, or bone marrow cultures may be used to isolate the Salmonella bacteria. 

2. Molecular tests (culture-independent diagnostic tests - CIDTs)

• PCR (Polymerase Chain Reaction) Tests: These tests detect Salmonella DNA in a sample and are becoming increasingly common due to their speed and sensitivity.
• Multiplex PCR Panels: Can detect Salmonella and other enteric pathogens (like Shigella and Yersinia) simultaneously, according to Medscape.
• Advantages: Rapid turnaround time (e.g., around 1 hour for some PCR tests) compared to traditional culture methods.
• Limitations: While CIDTs can quickly identify Salmonella, the New Mexico Department of Health notes they don't provide information on antibiotic resistance, necessitating follow-up with culture for this purpose. 

3. Antibody tests (serologic tests)

• Widal Test: Measures antibodies (O and H antigens) against Salmonella typhi, the bacteria causing typhoid fever. However, per Medscape its diagnostic value is limited by poor sensitivity, inability to distinguish between different antibody classes, and cross-reactivity with other Salmonella species and pathogens.
• Newer Antibody Tests (e.g., Typhidot, Tubex): Directly detect IgM antibodies to specific S. typhi antigens, showing promise but needing further evaluation.
• Limitations: Serologic tests are often unreliable and not generally recommended for diagnosing acute nontyphoidal Salmonella infections.

Treatment

Treating nontyphoidal Salmonella infections

1. Supportive care

• Most healthy individuals with non-typhoidal salmonella infections experience self-limiting symptoms that resolve within a few days to a week and don't require specific medical treatment.
• The primary focus for treatment is rehydration to prevent or address dehydration caused by diarrhea and vomiting.
• Drink plenty of fluids like water, oral rehydration solutions (especially for infants and children, according to the CDC), or clear broths.
• Rest is also important to allow the body to recover. 

2. Medications

• Anti-diarrheal medications: Drugs like loperamide (Imodium A-D) can help relieve cramping, but they may prolong the diarrhea associated with Salmonella infection. Consult a doctor before using them, especially if you have bloody diarrhea, fever, or diarrhea lasting over two days.
• Antibiotics: Generally, antibiotics are not recommended for uncomplicated non-typhoidal Salmonella gastroenteritis as they don't shorten the duration of diarrhea and may prolong shedding of the bacteria and increase the risk of relapse.
• Antibiotics are recommended for individuals at higher risk of invasive disease or those with severe or systemic infections, according to the CDC. These groups include:
  • Infants under 3 months of age.
  • Older adults and those with weakened immune systems (e.g., people with cancer, HIV/AIDS, or transplant recipients).
  • Individuals with severe diarrhea, blood infections (bacteremia), or infections that have spread beyond the intestines (extra-intestinal infections).
  • People with certain medical conditions like heart disease or major joint disease.
• Recommended antibiotics, depending on susceptibility testing and patient factors, can include:
  • Ciprofloxacin.
  • Azithromycin. Azithromycin is often preferred due to lower resistance development, according to a systematic review published in PubMed.
  • Ceftriaxone.
  • Trimethoprim/sulfamethoxazole (TMP/SMX).
  • Amoxicillin (as an alternative agent, particularly in children).
• Surgery may be needed in rare cases for complications like abscesses, infected aneurysms, or endocarditis.

Residuals

After a nontyphoidal Salmonella infection, most individuals recover fully within a week, although it may take several months for bowel habits to normalize. While most individuals recover completely, some may experience lingering effects and complications, including: 

1. Post-infectious irritable bowel syndrome (PI-IBS)

• Some individuals develop IBS symptoms after a bout of gastroenteritis caused by various bacteria, including Salmonella.
• PI-IBS is characterized by persistent abdominal discomfort, bloating, and diarrhea, even after the infection has cleared.
• The risk of developing IBS increases significantly after gastrointestinal infection and can remain elevated for several years.
• The development of PI-IBS involves factors such as changes in gut flora, persistent inflammation, and altered motility.
• There's a potential link between PI-IBS and autoimmunity, where the immune system, triggered by the infection, mistakenly attacks the body's tissues, according to IBS-Smart.
• Some patients experience malabsorption syndrome, where the small intestine doesn't effectively digest and absorb nutrients. 

2. Reactive arthritis

• This involves joint pain and inflammation, typically occurring weeks or even months after the initial infection.
• It's more common in individuals between 15 and 35 years old and those with the HLA-B27 gene.
• Reactive arthritis can cause symptoms like joint pain, eye irritation, and painful urination.
• While most cases resolve within a few months, some can become chronic and last for years. 

3. Other extra-intestinal infections

• In some cases, Salmonella can spread beyond the intestines and infect other organs or body systems, such as the blood (bacteremia), bones (osteomyelitis), or joints (septic arthritis).
• These invasive infections are more likely to occur in infants, older adults, and individuals with weakened immune systems.
• Such infections can be serious and potentially life-threatening. 

4. Dyspepsia

• Some individuals may experience persistent symptoms of dyspepsia, such as nausea, abdominal discomfort, and early satiety. 

Important note: While these conditions are possible residuals of nontyphoidal Salmonella infection, they are not universal. Most individuals recover without these long-term complications. If you experience any persistent or concerning symptoms after a Salmonella infection, it is crucial to consult with a healthcare professional for diagnosis and appropriate management.