(See also Overview of Salmonella Infections Overview of Salmonella Infections The genus Salmonella is divided into 2 species, S. enterica and S. bongori, which include > 2400 known serotypes. Some of these serotypes are named. In such cases, common usage sometimes shortens... read more .)
Nontyphoidal Salmonella infections are common and remain a significant public health problem in the US. Many serotypes of Salmonella have been given names and are referred to informally as if they were separate species even though they are not. Most nontyphoidal Salmonella infections are caused by S. enterica subspecies enterica serotype Enteritidis, S. Typhimurium, S. Newport, S. Heidelberg, and S. Javiana.
Human disease occurs by direct and indirect contact with numerous species of infected animals, the foodstuffs derived from them, and their excreta. Contaminated meat, poultry, raw milk, eggs, egg products, and water are common sources of Salmonella. Other reported sources include infected pet turtles and reptiles, carmine red dye, and contaminated marijuana.
Subtotal gastrectomy, achlorhydria (or ingestion of antacids), hemolytic conditions (eg, sickle cell anemia Sickle Cell Disease Sickle cell disease (a hemoglobinopathy) causes a chronic hemolytic anemia occurring almost exclusively in blacks. It is caused by homozygous inheritance of genes for hemoglobin (Hb) S. Sickle-shaped... read more , Oroya fever Oroya Fever and Verruga Peruana Oroya fever and verruga peruana are infections caused by the gram-negative bacterium Bartonella bacilliformis. Oroya fever occurs after initial exposure; verruga peruana occurs after recovery... read more , malaria Malaria Malaria is infection with Plasmodium species. Symptoms and signs include fever (which may be periodic), chills, rigors, sweating, diarrhea, abdominal pain, respiratory distress, confusion, seizures... read more ), bartonellosis Overview of Bartonella Infections Bartonella species are gram-negative bacteria previously classified as Rickettsiae. They are facultative intracellular organisms that typically live within red blood cells (RBCs) and endothelial... read more , splenectomy, louse-borne relapsing fever Relapsing Fever Relapsing fever is a recurring febrile disease caused by several species of the spirochete Borrelia and transmitted by lice or ticks. Symptoms are recurrent febrile episodes with headache, myalgia... read more , cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic fibrosis that has resulted in widespread distortion of normal hepatic architecture. Cirrhosis is characterized by regenerative nodules surrounded by dense... read more , leukemia Overview of Leukemia Leukemia is a malignant condition involving the excess production of immature or abnormal leukocytes, which eventually suppresses the production of normal blood cells and results in symptoms... read more , lymphoma Overview of Lymphoma Lymphomas are a heterogeneous group of tumors arising in the reticuloendothelial and lymphatic systems. The major types are Hodgkin lymphoma and non-Hodgkin lymphoma (see table Comparison of... read more , and HIV infection Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more are all risk factors for Salmonella infection.
Diseases caused by nontyphoidal Salmonella species
Each Salmonella serotype can cause any or all of the clinical syndromes described below, although given serotypes tend to produce specific syndromes. Enteric fever, for instance, is caused by S. Paratyphi types A, B, and C.
An asymptomatic carrier state may also occur. However, carriers are rare and do not appear to play a major role in large outbreaks of nontyphoidal gastroenteritis. Persistent shedding of organisms in the stool for ≥ 1 year occurs in only 0.2 to 0.6% of patients with nontyphoidal Salmonella infections.
Symptoms and Signs
Salmonella infection may manifest as
Gastroenteritis usually starts 12 to 48 hours after ingestion of organisms, with nausea and cramping abdominal pain followed by diarrhea, fever, and sometimes vomiting. Usually, the stool is watery but may be a pastelike semisolid. Rarely, mucus or blood is present. The disease is usually mild, lasting 1 to 4 days. Occasionally, a more severe, protracted illness occurs. About 10 to 30% of adults develop reactive arthritis Reactive Arthritis Reactive arthritis is an acute spondyloarthropathy that often seems precipitated by an infection, usually genitourinary or gastrointestinal. Common manifestations include asymmetric arthritis... read more weeks to months after diarrhea stops. This disorder causes pain and swelling, usually in the hips, knees, and Achilles tendon.
Enteric fever is a less severe form than typhoid Typhoid Fever Typhoid fever is a systemic disease caused by the gram-negative bacterium Salmonella enterica serotype Typhi (S. Typhi). Symptoms are high fever, prostration, abdominal pain, and a rose-colored... read more ; it is characterized by fever, prostration, and septicemia.
Bacteremia is relatively uncommon in patients with gastroenteritis, except in infants and older people. However, S. Choleraesuis, S. Typhimurium, and S. Heidelberg, among others, can cause a sustained and frequently lethal bacteremic syndrome lasting ≥ 1 week, with prolonged fever, headache, malaise, and chills but rarely diarrhea. Patients may have recurrent episodes of bacteremia or other invasive infections (eg, septic arthritis) due to Salmonella. Recurrent or multiple episodes of Salmonella infection in a patient without other risk factors should prompt HIV testing.
Focal Salmonella infection can occur with or without sustained bacteremia, causing pain in or referred from the involved organ—the gastrointestinal tract (liver, gallbladder, appendix), endothelial surfaces (eg, atherosclerotic plaques, ileofemoral or aortic aneurysms, heart valves), pericardium, meninges, lungs, joints, bones, genitourinary tract, or soft tissues. Preexisting solid tumors are occasionally seeded and develop abscesses that may, in turn, become a source of Salmonella bacteremia. S. Choleraesuis and S. Typhimurium are the most common causes of focal infection.
Diagnosis of nontyphoidal Salmonella infections is by isolating the organism from stool or another infected site. In bacteremic and focal forms, blood cultures are positive, but stool cultures may be negative.
Antibiotic resistance is more common with nontyphoidal Salmonella than with S. Typhi, and antimicrobial susceptibility testing is important.
In patients with gastroenteritis, stool specimens stained with methylene blue often show white blood cells, indicating inflammatory colitis.
Ciprofloxacin, azithromycin, ceftriaxone, or trimethoprim/sulfamethoxazole (TMP/SMX) only for high-risk patients and patients with systemic or focal infections
Uncomplicated gastroenteritis due to nontyphoidal Salmonella infections is treated symptomatically with oral or IV fluids (see treatment of gastroenteritis Treatment Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. Most cases are infectious, although gastroenteritis may occur after ingestion of drugs and chemical... read more ).
Antibiotics do not hasten resolution of gastroenteritis, may prolong excretion of the organism, and are unwarranted in uncomplicated cases. However, in older nursing home residents, infants, and patients with hemoglobinopathies, HIV infection, or other immunocompromising conditions, increased mortality dictates treatment with antibiotics. Acceptable antibiotic regimens include the following:
TMP/SMX 5 mg/kg (of the TMP component) orally every 12 hours for children
Ciprofloxacin 500 mg orally every 12 hours for adults
Azithromycin 500 mg orally on day 1 followed by 250 mg once a day for 4 days for adults
Ceftriaxone 2 g IV once a day for 7 to 10 days for adults
Pearls & Pitfalls
Nonimmunocompromised patients should be treated for 3 to 5 days; patients with AIDS may require prolonged suppression to prevent relapses.
Systemic or focal disease should be treated with antibiotic doses as for typhoid fever Treatment Typhoid fever is a systemic disease caused by the gram-negative bacterium Salmonella enterica serotype Typhi (S. Typhi). Symptoms are high fever, prostration, abdominal pain, and a rose-colored... read more . Sustained bacteremia is generally treated for 4 to 6 weeks.
Abscesses should be drained surgically. At least 4 week of antibiotic therapy should follow surgery.
Infected aneurysms and heart valves and bone or joint infections usually require surgical intervention and prolonged courses of antibiotics.
The prognosis is usually good, unless severe underlying disease is present.
Asymptomatic carriage is usually self-limited, and antibiotic treatment is rarely required. In unusual cases (eg, in food handlers or health care workers), eradication may be attempted with oral ciprofloxacin 500 mg every 12 hours for 1 month. Follow-up stool cultures should be obtained in the weeks after drug administration to document elimination of Salmonella.
Preventing contamination of foodstuffs by infected animals and humans is paramount. Preventive measures for travelers Traveler’s diarrhea Appropriate planning reduces the risks associated with travel, including foreign travel. Prior to travel, patients and their medical providers should review planned itineraries and relevant... read more also apply to most other enteric infections.
Case reporting is essential.
Nontyphoidal Salmonella infections are common and result from direct and indirect contact with numerous species of infected animals, the foodstuffs derived from them, and their excreta.
Clinical syndromes include gastroenteritis, enteric fever, and focal infections; bacteremia occasionally occurs.
Diagnose using cultures.
For uncomplicated gastroenteritis, antibiotics are unnecessary; they do not hasten resolution and may prolong excretion of the organism.
Treat high-risk patients (eg, older nursing home residents, infants, patients with hemoglobinopathies, HIV infection, or other immunocompromising conditions) with antibiotics, such as ciprofloxacin, azithromycin, ceftriaxone, or trimethoprim/sulfamethoxazole (TMP/SMX).
An asymptomatic carrier state may occur, but carriers do not play a major role in outbreaks, and treatment with antibiotics is rarely indicated.