Basics
Description
Salmonella isolates are broadly divided into the following: 1) nontyphoidal serotypes, with illness ranging from uncomplicated gastroenteritis to meningitis; and 2) typhoidal serotypes, responsible for typhoid and paratyphoid fever (collectively called enteric fever). ‚
Epidemiology
- Salmonella is a leading cause of foodborne infection in the United States and worldwide.
- Reservoirs
- Nontyphoidal Salmonella serotypes are commonly found in agricultural products, particularly cattle, poultry, and eggs. Less common sources include produce, dairy products, and processed foods. Humans may asymptomatically shed the bacteria for weeks, even months. Reptiles are another well-recognized reservoir for infection.
- Typhoidal serotypes are found only in humans with acute or chronic infection.
- Transmission
- Spread occurs via the fecal " “oral route. Food and water contamination is the most common mechanism of exposure, followed by direct contact with contaminated surfaces and live animals.
- Salmonella generally requires a high-bacterial inoculum to cause infection.
- Age/season: Salmonella infections are most common in children younger than 4 years of age and during the summer months.
Risk Factors
- Young infants (especially those <3 months of age), children with sickle cell disease (SCD), human immunodeficiency virus (HIV), malignancy, and other immunocompromised conditions are at high risk for extraintestinal complications from nontyphoidal Salmonella gastroenteritis.
- Travel to underdeveloped countries
General Prevention
- Proper cleaning of food preparation surfaces and careful hand hygiene, particularly when handling foods at risk for Salmonella contamination
- Foods that frequently harbor Salmonella, such as meat, poultry, and eggs, require thorough cooking.
- Children <5 years old, and all those with high-risk conditions, should avoid contact with reptiles (e.g., lizards, snakes, turtles).
- Vaccines for typhoid fever have an efficacy of 50 " “80% and are recommended for the following: 1) travel to endemic areas and 2) close contacts of carriers. Available vaccines include the following:
- Ty21a, live vaccine for children ≥6 years of age; given PO every other day for 4 doses
- ViCPS, inactivated vaccine for children ≥2 years of age; given as a single IM dose
Etiology
Salmonella is classified into 2 species: Salmonella enterica and Salmonella bongori. Species are further divided into 1 of over 2,500 serotypes. ‚
- Common nontyphoidal serotypes include the following: Salmonella enterica ser Enteritidis, Salmonella enterica ser Typhimurium, Salmonella enterica ser Newport, and Salmonella enterica ser Heidelberg.
- Typhoidal serotypes include the following: Salmonella enterica ser Typhi and Salmonella enterica ser Paratyphi.
Commonly Associated Conditions
Following infection of the intestinal epithelium, Salmonella strains present with a variety of clinical manifestations. ‚
- Acute gastroenteritis is the most common illness involving nontyphoidal serotypes:
- Diarrhea is often watery but can be inflammatory with varying amounts of mucus and/or blood.
- The incubation period is 12 " “48 hours, and illness usually resolves within 3 " “5 days. Asymptomatic shedding is common with a mean duration of 5 weeks " ”longer in infants.
- Transient bacteremia (nontyphoidal)
- Bacteremia occurs in up to 5% of infected immunocompetent children and in 10% or more of high-risk patients. Young infants are generally at higher risk for bacteremia.
- The most common serotypes associated with bacteremia include Salmonella Enteritidis, Salmonella Heidelberg, and Salmonella Typhimurium.
- Bacteremia can result in localized extraintestinal infection.
- Localized extraintestinal infection (nontyphoidal)
- Local infections occur in 3 " “5% of otherwise healthy bacteremic children and in up to 30% of high-risk bacteremic patients.
- Infections include meningitis, septic arthritis, osteomyelitis, and pneumonia.
- Infants <3 months of age are at higher risk for meningitis.
- Enteric fever (typhoid and paratyphoid fever)
- The most important serotypes are Salmonella Typhi, followed by the less frequent and milder Parathypi strain.
- Incubation is usually 7 " “10 days but can be 3 " “60 days.
- The clinical course is often insidious with progression of disease over 3 " “4 weeks. Week 1 " “2: Fever, headache, myalgia, abdominal pain, and listlessness are common. Diarrhea occurs in less than half of patients, and constipation is common. Week 2 " “3: Fever increases, and rose spots (maculopapular rash) may appear. Splenomegaly and respiratory symptoms may develop. Week 3 " “4: Fever gradually improves, however, serious complications, such as intestinal perforation, may develop at this time.
Diagnosis
History
- Exposure history: nontyphoidal
- Recent contact with farm animals (e.g., fairs and petting zoos) or reptiles. Reptiles may pose a risk even without direct contact.
- Recent travel to underdeveloped regions of the world
- Close contacts with recent gastroenteritis
- Consumption of raw milk or undercooked eggs
- Exposure history: typhoidal
- Travel to underdeveloped countries or close contact to persons recently living in, or visiting, endemic regions.
- Clinical history: nontyphoidal
- Vomiting appears in half of infected children.
- Fever (up to 39 ‚ °C) and abdominal pain are common complaints.
- Stools with mucus and/or blood should raise suspicion for Salmonella as well as other common bacterial intestinal pathogens. Blood in the stool appears in less than 1/3 of patients with Salmonella.
- Signs or symptoms indicative of sepsis, meningitis, osteomyelitis, or septic arthritis " ”especially in young infants and other high-risk patients " ”should raise suspicion for Salmonella.
- A positive blood culture with a gram-negative rod may precede the diagnosis of Salmonella gastroenteritis.
- Clinical history: typhoidal
- Half of infected patients present with constipation. Only 1/3 of children have diarrhea.
- Fever ranges from 39 ‚ ° to 40 ‚ °C and worsens through the first and second week of illness.
- Rash and mental status changes may be present.
- In children <5 years, enteric fever may appear as a nonspecific viral illness.
Physical Exam
- Nontyphoidal infections
- Examine for signs of dehydration.
- Children with uncomplicated bacteremia may be clinically indistinguishable from nonbacteremic patients.
- Fever can be absent in children with bacteremia, especially young infants.
- Examine for localized signs of infection in bone and joints.
- Very young infants with Salmonella may present with a normal exam, including those with meningitis.
- When possible, directly inspect stool for gross blood and mucus.
- Enteric fever
- Patients with high fever may exhibit a relative bradycardia.
- A coated tongue may be noted.
- Hepatomegaly and splenomegaly are common.
- 2 " “4 mm maculopapular lesions (rose spots) appear in up to 25% of patients.
- Rales and rhonchi can be present.
Diagnostic Tests & Interpretation
Lab
- Testing involves the following:
- Basic blood chemistries may reveal dehydration and electrolyte imbalances.
- WBC counts vary widely and are generally not helpful in diagnosis.
- Bilirubin and serum transaminases may be elevated with enteric fever.
- Stool culture is the most sensitive test for nontyphoidal gastrointestinal infection. Preliminary culture results reveal nonlactose fermenting, H2S-producing colonies.
- Fecal leukocyte and stool guaiac tests have limited sensitivity and specificity for diagnosing bacterial gastroenteritis.
- Blood cultures are positive in up to 5% of nontyphoidal infections and 60 " “80% of patients with enteric fever.
- Bone marrow aspirations are positive in 80 " “95% of patients with typhoid fever.
- Routine bacterial culture of urine, CSF, or bone or joint aspirates should be obtained when clinically indicated.
Differential Diagnosis
- Illnesses that appear similar to nontyphoidal Salmonella infection
- Acute gastroenteritis caused by Shigella, Escherichia coli, Campylobacter, and Yersinia is indistinguishable from Salmonella.
- Clostridium difficile causes watery and inflammatory diarrhea, especially in children >2 years of age.
- Norovirus, rotavirus, Cryptosporidium, and Giardia are common causes of watery diarrhea.
- Allergic colitis
- Inflammatory bowel disease
- Bone and joint infection due to Staphylococcus aureus, group A strep, pneumococcus, and Kingella
- Enteric fever from Salmonella may appear similar to the following:
- Appendicitis
- Brucellosis
- Dengue fever
- Malaria
- Nonspecific viral illness
Treatment
Medication
- Antimicrobials are not indicated for uncomplicated nontyphoidal gastroenteritis, and their use has been associated with prolonged carriage.
- Antimicrobial therapy is indicated for the following:
- High-risk patients with nontyphoidal gastroenteritis pending blood culture results. These include the following: 1) infants <3 months of age; 2) children with HIV, SCD, and 3) those with malignancy and/or receiving immunosuppressive therapy.
- Patients with known or suspected nontyphoidal bacteremia or localized infection
- Patients with known or suspected enteric fever
- Antimicrobial choice
- Ceftriaxone or cefotaxime is the preferred drug for empirical therapy of nontyphoidal and typhoidal infections while awaiting blood culture and sensitivity results.
- If shown to be susceptible, amoxicillin or trimethoprim/sulfamethoxazole (TMP/SMX) may be used in high-risk patients with uncomplicated nontyphoidal gastroenteritis and negative blood cultures.
- Antimicrobial selection should be based on culture results when available. High rates of resistance occur with ampicillin and TMP/SMX.
- Quinolones are generally active but not approved for patients <18 years of age.
- Corticosteroids may provide benefit to critically ill patients with enteric fever.
Inpatient Considerations
Initial Management
- Patients with dehydration and electrolyte abnormalities require appropriate volume replacement.
- Antimotility agents are generally avoided for all forms of infectious diarrhea in children.
- Consult orthopedics for management of suspected bone and joint infections.
- Administer antimicrobials only for specific clinical indications.
Ongoing Care
Follow-up Recommendations
- Acute nontyphoidal gastroenteritis
- Encourage appropriate oral rehydrating fluids and monitor for signs and symptoms of dehydration.
- Monitor for invasive complications, especially among high-risk patients.
- Apprise patients and/or families of the risk for prolonged asymptomatic shedding.
- Instruct patients and families in proper hand hygiene.
- Enteric fever
- Fever can persist up to 7 days after starting appropriate antimicrobial therapy.
- Monitor for serious complications such as intestinal bleeding, even after the patient appears to be improving.
- Monitor for evidence of relapse.
- Instruct patients and families in proper hand hygiene.
Alert
- Serious complications of enteric fever can present as the patient appears to be improving.
- Even with appropriate therapy, patients with enteric fever may relapse 2 " “3 weeks after the initial fever resolves.
Prognosis
- Noninvasive nontyphoidal gastroenteritis is typically a self-limiting infection.
- Individuals often shed the organism for weeks, and a small number of patients may continue to shed for >1 year.
- Relapse of typhoid fever occurs in 4 " “20% of patients up to 3 weeks after the fever resolves.
Complications
- Dehydration is the most common complication caused by acute gastroenteritis.
- Nontyphoidal Salmonella gastroenteritis may be complicated by the following:
- Bacteremia, especially in high-risk patients
- Osteomyelitis and septic arthritis. Patients with sickle cell disease are particularly susceptible.
- Meningitis. The course is frequently severe and may be associated with abscess formation and relapse.
- Other infectious complications include pneumonia, pyelonephritis, and pericarditis.
- Enteric fever complications include intestinal perforation and hemorrhage, cholecystitis, hepatitis encephalopathy, pneumonia, myocarditis, shock, and disseminated intravascular coagulation.
Additional Reading
- Bar-Meir ‚ M, Raveh ‚ D, Yinnon ‚ AM, et al. Non-Typhi Salmonella gastroenteritis in children presenting to the emergency department: characteristics of patients with associated bacteraemia. Clin Micrbiol Infect. 2005;11(8):651 " “655. ‚ [View Abstract]
- Bhutta ‚ ZA. Current concepts in the diagnosis and treatment of typhoid fever. BMJ. 2006;333(7558):78 " “82. ‚ [View Abstract]
- Cheng ‚ LH, Crim ‚ SM, Cole ‚ CR, et al. Epidemiology of infant salmonellosis in the United States, 1996-2008: a Foodborne Diseases Active Surveillance Network Study. J Ped Infect Dis. 2003;2(3):232 " “239.
- Christenson ‚ JC. Salmonella infections. Pediatr Rev. 2013;34(9):375 " “383. ‚ [View Abstract]
- Geme ‚ JW III, Hodes ‚ HL, Marcy ‚ SM, et al. Consensus: management of Salmonella infection in the first year of life. Pediatr Infect Dis J. 1998;7(9):615 " “621. ‚ [View Abstract]
Codes
ICD09
- 003.9 Salmonella infection, unspecified
- 003.0 Salmonella gastroenteritis
- 002.0 Typhoid fever
- 003.21 Salmonella meningitis
ICD10
- A02.9 Salmonella infection, unspecified
- A02.0 Salmonella enteritis
- A01.00 Typhoid fever, unspecified
- A02.21 Salmonella meningitis
SNOMED
- 302231008 Salmonella infection (disorder)
- 42338000 Salmonella gastroenteritis (disorder)
- 186090001 Typhoid and paratyphoid fevers (disorder)
- 77645007 Salmonella meningitis (disorder)
- 302229004 Salmonella food poisoning
FAQ
- Q: When can children infected with Salmonella return to day care or school?
- A: In general, infants and children with nontyphoidal Salmonella infection may return to day care or school 24 hours after their diarrhea has resolved. Repeat stool cultures are not recommended because asymptomatic shedding is common, and the risk of spread is low. Health officials may recommend documenting a negative stool culture if there are obvious concerns regarding a child 's hygiene. Children with S. Typhi infection who are ≥5 years of age and asymptomatic for over 24 hours, may attend school without repeating stool cultures. For children <5 years of age with S. Typhi, it is generally required that the child be asymptomatic and have 3 negative stool cultures before returning to day care. Most health departments adopt this approach.