MI3.5-8 | Enteric Fever, PUO & Sepsis — Summary & Reflection

REFLECT

Return to the opening case: the student with 10 days of fever and a Widal showing O 1:160, H 1:80.

• Is this a significant O titre in an Indian endemic area?
• The blood culture (taken Day 12) grew MDR S. Typhi. Why was Day 12 still useful for blood culture?
• If this patient had been a cook presenting 6 months after a previous typhoid episode, with no current symptoms, which investigation pathway would you use to evaluate carrier status?
• How would you approach PUO in a patient with similar fever duration if enteric fever workup is negative?

Write out the investigation plan before moving on.

KEY TAKEAWAYS

PUO:
- Defined as fever >38.3°C for >3 weeks without diagnosis after 1 week thorough workup
- Infective causes dominate in India: tuberculosis, enteric fever, malaria, liver abscess, IE
- Investigate systematically: repeated blood cultures, serology panel, bone marrow biopsy/culture, imaging

Enteric Fever:
- Caused by S. Typhi (typhoid) and Paratyphi A/B/C; reservoir = humans (chronic biliary carrier)
- Pathogenesis: M-cell → Peyer's patches → intracellular macrophage survival → primary bacteraemia → liver/spleen/gallbladder seeding → secondary bacteraemia → ulceration
- Clinical: step-ladder fever, relative bradycardia, rose spots, splenomegaly; perforation in Week 3–4
- Resistance: MDR, NARST, XDR S. Typhi — culture is essential to guide antibiotic selection

Test selection by week:
- Week 1–2: Blood culture (gold standard); Bone marrow at any stage (90% sensitivity)
- Week 3+: Widal (paired sera); Stool/urine culture
- Carrier: Vi agglutination ≥ 1:20 + 3 stool cultures

Widal interpretation:
- High O + low H = acute infection; High H + low O = past infection or TAB vaccination
- Always use paired sera (4-fold rise) for definitive diagnosis; endemic baseline titres are high in India
- Newer alternatives: Typhidot-M, Tubex, PCR