Non-Typhoidal Salmonellosis
On this page
Direct answer
Non-typhoidal salmonellosis is infection by Salmonella serovars other than Salmonella Typhi and Salmonella Paratyphi, usually causing self-limiting gastroenteritis from contaminated food such as poultry, eggs and meat. It becomes dangerous in immunocompromised patients, the very young, the elderly and people with sickle cell disease, where it can cause bacteraemia and metastatic infection such as osteomyelitis. Most gastroenteritis needs only fluids, and antibiotics are reserved for high-risk patients.
What you must remember
- Serovars: Salmonella Typhimurium and Salmonella Enteritidis are common non-typhoidal serovars, unlike Salmonella Typhi, which causes enteric fever.
- Source: undercooked poultry, eggs, meat, contaminated milk and produce, along with animal reservoirs such as poultry and reptiles.
- Gastroenteritis: diarrhoea, abdominal cramps and fever usually begin within a day or so of exposure and resolve within days in a healthy host.
- Bacteraemia: most likely in infants, the elderly and patients with HIV or other immune deficiency, so blood cultures are needed when systemically unwell.
- Sickle cell disease: functional asplenia predisposes to bacteraemia and Salmonella osteomyelitis, a classic association in children.
- Diagnosis: stool culture on selective media, with H2S-producing colonies on XLD agar, and blood culture when the patient is systemically unwell.
- Antibiotics: reserved for immunocompromised patients, bacteraemia, severe illness, infants, the elderly and sickle cell disease, with ceftriaxone or a fluoroquinolone commonly used.
Deciding whether a patient needs antibiotics
Most cases of non-typhoidal salmonellosis are settled by fluids alone, so the decision turns on the host rather than the stool. The steps below move from the healthy adult to the patient who needs the most careful review.
- Gastroenteritis in a healthy adult: diarrhoea and cramps that resolve within days are managed with fluids and no antibiotic, since treatment may prolong faecal shedding.
- Immunocompromised host: patients with HIV, malignancy or immunosuppressive therapy who have fever or bacteraemia need blood cultures and treatment, even when gut symptoms are mild.
- Sickle cell disease: any Salmonella infection in sickle cell disease warrants a search for bacteraemia and osteomyelitis, since asplenia makes the infection more invasive.
- Bone pain or focal signs: persistent bone pain, joint swelling or a focal infection prompts imaging, because osteomyelitis classically involves the long bones of children with sickle cell disease.
- Choose and time the antibiotic: ceftriaxone or a fluoroquinolone is chosen according to susceptibility and patient factors, with longer courses for bacteraemia and metastatic infection.
- Look for a focus: fever that persists despite treatment should prompt a search for endovascular, bone or other deep infection rather than an assumption that the gut is the only site.
Where the exam tries to catch you
Examiners test whether the student separates the self-limiting gut infection from the invasive disease in vulnerable hosts. The traps below are the errors that cost marks most often in this area.
- Trap: every Salmonella infection needs antibiotics Correct: uncomplicated gastroenteritis in a healthy person settles with fluids, and antibiotics are reserved for high-risk patients.
- Trap: non-typhoidal Salmonella and Salmonella Typhi cause the same disease Correct: non-typhoidal serovars cause gastroenteritis and invasive disease in vulnerable hosts, while Salmonella Typhi causes systemic enteric fever in humans, with no animal reservoir.
- Trap: a sickle cell patient with Salmonella gastroenteritis needs only fluids Correct: sickle cell disease predisposes to bacteraemia and osteomyelitis, so these patients need evaluation for an invasive focus.
Frequently asked questions
Which Salmonella serovars cause non-typhoidal salmonellosis?
Serovars such as Salmonella Typhimurium and Salmonella Enteritidis commonly cause non-typhoidal salmonellosis, which is distinct from the enteric fever caused by Salmonella Typhi. Non-typhoidal serovars are usually acquired from contaminated poultry, eggs, meat or animal sources.
Why is non-typhoidal salmonellosis more dangerous in sickle cell disease?
Non-typhoidal salmonellosis is more dangerous in sickle cell disease because functional asplenia makes bacteraemia and metastatic infection more likely. Salmonella osteomyelitis is a classic complication, especially in the long bones of children.
When should antibiotics be given for non-typhoidal salmonellosis?
Antibiotics for non-typhoidal salmonellosis are reserved for infants, the elderly, immunocompromised patients, severe illness, bacteraemia and sickle cell disease. Uncomplicated gastroenteritis in a healthy adult settles with fluids alone.
Which test confirms non-typhoidal salmonellosis?
Stool culture on selective media confirms non-typhoidal salmonellosis, and blood culture is added when the patient is systemically unwell. Salmonella colonies on XLD agar often produce hydrogen sulphide, which appears as black centres.
Are antibiotics routinely used for uncomplicated non-typhoidal salmonellosis?
Antibiotics are not routinely given for uncomplicated non-typhoidal salmonellosis, because they may prolong faecal shedding. Asymptomatic carriers are not usually treated in the community, so antibiotics are targeted at high-risk patients.