Enteric fever and invasive bacterial enteritis — branching viva

Opening (2-3 minutes)

Examiner: Two children with fever and abnormal stools. Walk me through how you separate them. [1]

Strong answer: I separate invasive from non-invasive disease. The 9-year-old has a stepwise fever with relative bradycardia, constipation and abdominal pain after travel to Pakistan — that is enteric fever until proven otherwise, and I draw blood culture before antibiotics. The 4-year-old has bloody diarrhoea with little fever after a farm visit — that is Shiga-toxin producing E. coli colitis until I prove otherwise, and I send stool, watch for haemolytic uraemic syndrome, and avoid routine antibiotics. [1] [12]

Branch A — Diagnosing enteric fever

Examiner: What is your diagnostic strategy for the 9-year-old? [1]

Strong answer: Blood culture is the gold standard and I take it before any antibiotic, repeating if negative and suspicion persists. If he has already had antibiotics, bone marrow culture has the highest yield. I send stool and urine cultures and a malaria film to exclude the key mimic. I do not rely on a single Widal test — it is insensitive and non-specific, and a negative or positive result does not decide management. [1]

Branch B — XDR and antibiotic choice

Examiner: He is from Pakistan. What does that mean for your antibiotic? [8]

Strong answer: Travel to Pakistan raises the probability of extensively drug-resistant typhoid — resistant to fluoroquinolones and third-generation cephalosporins. I start oral azithromycin empirically for uncomplicated disease, with meropenem reserved for severe, complicated or refractory XDR. For non-XDR fluoroquinolone-resistant strains, azithromycin or ceftriaxone is reasonable. I narrow once susceptibilities return and treat for seven to fourteen days. [8] [4]

Branch C — Complications

Examiner: In week three he develops sudden severe abdominal pain and a rigid abdomen. What is happening? [1]

Strong answer: Intestinal perforation through an ulcerated Peyer's patch, with secondary peritonitis — a surgical emergency in weeks three to four of typhoid. I keep him nil by mouth, gain intravenous access, give fluid resuscitation and broad-spectrum antibiotics covering gut flora, and obtain urgent surgical review and imaging. I do not attribute new symptoms to the original gastroenteritis label. [1]

Branch D — The STEC-HUS danger

Examiner: Back to the 4-year-old. Five days on she is pale with petechiae and oliguria. Reason with me. [12]

Strong answer: Evolving haemolytic uraemic syndrome from STEC. I check a full blood count and film (microangiopathic haemolytic anaemia with schistocytes), platelets (thrombocytopenia), creatinine and electrolytes (acute kidney injury) and LDH. I avoid routine antibiotics and nephrotoxins, give careful intravenous fluids to protect renal perfusion, and refer early to nephrology for supportive care and dialysis if needed. [12]

Branch E — Prevention

Examiner: How do you prevent the next case? [5]

Strong answer: The typhoid conjugate vaccine — Vi-tetanus toxoid conjugate — is the prevention cornerstone, shown to have roughly eighty-seven per cent efficacy in the controlled human infection model (Jin 2017) and confirmed in field trials. The WHO recommends routine use in endemic countries and I advise it for travellers. Safe water, sanitation, hand hygiene and food safety are the structural foundation. Enteric fever and shigellosis are notifiable, so I notify public health and trace contacts. [5]

Examiner scoring cues

Pass: invasive-versus-non-invasive framing; blood culture before antibiotics; bone marrow if pre-treated; XDR-aware empiric choice; recognition of perforation and HUS; no routine antibiotics in STEC; vaccine and notification. [1] [4] [12] Fail: empiric antibiotics before culture; reliance on Widal; missed XDR; routine antibiotics in STEC; rigid abdomen attributed to "gastro"; no vaccine or public-health plan. [8] [13]