Nontyphoidal salmonella
Flagellated, facultatively anaerobic Gram-negative bacilli of the family Enterobacteriaceae (chiefly *Salmonella enterica* serovars other than Typhi and Paratyphi) that typically cause self-limited gastroenteritis but can produce invasive bacteremia, particularly in immunocompromised hosts.
Organism Card
| Domain | Must know |
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| Identity |
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| Lab discriminator |
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| Reservoir / transmission |
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| Clinical syndromes |
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| Diagnosis |
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| Treatment |
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| Prevention |
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| Classic traps |
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Exam Intelligence
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GC 103 Fever after Travelling [Handout]: Explicitly states fluoroquinolone resistance is increasingly encountered; antibiotics of choice include 3rd-gen cephalosporins (ceftriaxone), azithromycin, and fluoroquinolones (if susceptible) — this framing applies to both typhoidal and Salmonella species broadly [4].
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GC 103: Travellers' diarrhoea is mainly bacterial (especially ETEC), but non-typhoidal Salmonella is a key differential when fever accompanies diarrhoea (ETEC typically non-febrile) [4].
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Jerry's immunodeficiencies notes (AOS-level): MSMD (Mendelian susceptibility to mycobacterial diseases) due to STAT1 / IFN-γ pathway defects → susceptible to mycobacteria AND Salmonella — this is a recurrent exam hook: "which organisms are these patients susceptible to?" [5].
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Adrian Lui Paeds Notes: Non-typhoidal serotypes are contrasted with typhoidal by emphasising animal hosts and typically milder disease [2].
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Ryan Ho Rheumatology: Salmonella (alongside Campylobacter, Yersinia) is a listed cause of erythema nodosum — a reactive phenomenon that can appear in exam vignettes as a post-infectious complication [7].
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Maksim Surgery Notes: Osteomyelitis in sickle cell disease → Salmonella is the classic pathogen (not S. aureus) [6].
- Salmonella Enteritidis vs enteric fever: The serotype name "Enteritidis" tricks students — it is a non-typhoidal serotype causing gastroenteritis, NOT enteric (typhoid) fever. Enteric fever = S. Typhi / Paratyphi only.
- Outbreak vignette timing: Vomiting ~1 hour post-meal with no fever → S. aureus preformed toxin. Diarrhoea + fever + cramps 6–72 h after eggs/poultry → Salmonella Enteritidis. Diarrhoea + fever 8–16 h after reheated meat → C. perfringens.
- Non-typhoidal Salmonella bacteraemia: Think of the patient — HIV/AIDS with low CD4, sickle cell, malignancy, corticosteroids, extremes of age.
- Reactive arthritis (Reiter syndrome) can follow non-typhoidal Salmonella GE — another post-infectious sequela alongside erythema nodosum.
2018 Fourth Summative MCQ Q26 [3]
"Thirty students from a secondary school but in different classes presented with vomiting with no fever approximately one hour after consuming a take-away egg and ham sandwich bought from a street vendor."
- Answer: I. Staphylococcus aureus (preformed enterotoxin; vomiting-predominant, ~1 h incubation, no fever).
- Discriminator: Salmonella Enteritidis (option H) is the trap — it would present later (6–72 h) with fever and diarrhoea, not isolated vomiting at 1 h. This question tests the S. aureus vs Salmonella outbreak distinction.
2019 Fourth Summative MCQ Q19 [9]
"Increased numbers of children and elderly presented with diarrhoea, abdominal cramps and fever to the Accident and Emergency Departments of several hospitals in a region in the past two months. Food history revealed that the only food most of the affected people consumed was frozen cheese cake purchased from a chain shop on Mother's Day."
- Answer: F. Listeria monocytogenes (ready-to-eat dairy product, prolonged outbreak over 2 months consistent with long incubation, affects vulnerable populations).
- Discriminator: Salmonella Enteritidis (option H) is again the near-miss — but the 2-month time course and frozen cheesecake (dairy, cold-chain product) favour Listeria, which grows at refrigerator temperatures. Salmonella outbreaks from a single-point source would cluster more tightly in time.
2019 Fourth Summative Mini Case, Case 1 [10]
23-year-old female with recurrent fever for 2 weeks after return from Bangladesh; constipation → non-bloody diarrhoea; fever 40°C with pulse 50 bpm (relative bradycardia); salmon-colored rashes on lower chest/abdomen. Blood and stool culture confirmed typhoid fever.
- This tests typhoidal Salmonella, but the vignette discriminators (stepwise fever, Faget sign = sphygmothermic dissociation, rose spots) are exactly what non-typhoidal Salmonella does NOT have. Students must know the contrast.
No other directly relevant past-paper stems for non-typhoidal Salmonella specifically were identified in the indexed context.
[1] Lecture slides: GC 103. Fever after travelling.pdf [2] Senior notes: Adrian Lui Pediatrics Notes.pdf, p. 484 [3] Past papers: 2018 Fourth Summative MCQ.pdf, p. 13 [4] Lecture slides: GC 103. Fever after travelling [Handout].pdf, p. 7 [5] Senior notes: Jerry's immunodeficiencies.pdf, pp. 2–3 [6] Senior notes: Maksim Surgery Notes.pdf, p. 275 [7] Senior notes: Ryan Ho Rheumatology.pdf, p. 157 [8] Senior notes: Block A - Generalised Lymphadenopathy.pdf, p. 3 [9] Past papers: 2019 Fourth Summative MCQ.pdf, p. 11 [10] Past papers: 2019 Fourth Summative Mini Case.pdf, p. 6
Salmonella typhi
Facultative intracellular, flagellated Gram-negative bacillus of the family Enterobacteriaceae that causes typhoid (enteric) fever, characterized by sustained bacteremia, fever, and potential intestinal perforation.
Shigella
Gram-negative, non-motile, facultatively anaerobic bacillus of the family Enterobacteriaceae that causes bacillary dysentery (shigellosis) characterized by invasive bloody, mucoid diarrhea.