Enteric fever and invasive bacterial enteritis — formative SAQs

SAQ 1 (10 marks)

A 9-year-old boy presents with a fever that has risen each day for six days after returning from Pakistan, with constipation, vague abdominal pain and a pulse of 88 at 39.5 degrees. He took two doses of a leftover antibiotic before presentation. [1]

1. List four features that support a diagnosis of enteric fever and state the diagnostic gold-standard test. (3) [1]
2. Explain how his travel history and prior antibiotics change your empiric management. (3) [8] [14]
3. Outline your stepwise antibiotic approach once blood culture is drawn, including the XDR scenario. (4) [4]

Model answer — SAQ 1

1. Stepwise fever climbing over 4-7 days with a relative bradycardia, abdominal pain with constipation, and hepatosplenomegaly or rose spots. The gold-standard test is blood culture (ideally before antibiotics); bone marrow culture has the highest yield when antibiotics have already been given. [1]

2. Travel to Pakistan raises the prior probability of extensively drug-resistant (XDR) typhoid. Prior antibiotics lower blood-culture yield, so send blood culture and, if negative, bone marrow culture; start an empiric regimen that covers XDR (oral azithromycin, or ceftriaxone where local guidance prefers it, with meropenem reserved for severe disease). Admit if he is unwell, dehydrated or shows complications. [8] [14]

3. Draw blood culture before any further antibiotic. For susceptible strains, a fluoroquinolone or azithromycin is first-line; for fluoroquinolone-resistant non-XDR strains, azithromycin or ceftriaxone. For XDR (resistant to fluoroquinolones and third-generation cephalosporins), oral azithromycin for uncomplicated disease and meropenem for severe, complicated or refractory disease. Narrow once susceptibilities return and treat for 7-14 days. Safety-net for perforation in weeks 3-4. [4]

SAQ 2 (10 marks)

A 4-year-old develops bloody diarrhoea with little fever after a farm visit. Five days later she is pale, with petechiae and reduced urine output. [12]

1. What complication has developed, and what three laboratory features confirm it? (3) [12]
2. Justify the standard recommendation against routine antibiotics in suspected STEC. (3) [12]
3. Outline your supportive management priorities and the monitoring through the danger window. (4) [12]

Model answer — SAQ 2

1. Haemolytic uraemic syndrome (HUS) following Shiga-toxin producing E. coli (STEC) colitis. The three laboratory features are microangiopathic haemolytic anaemia (with schistocytes on the film and raised LDH), thrombocytopenia, and acute kidney injury (rising creatinine). Send stool for Shiga toxin and E. coli O157 culture. [12]

2. Some antibiotics, particularly DNA-damaging agents, may increase Shiga toxin release and the risk of HUS; the evidence is mixed and no agent has been shown to prevent HUS. The defensible position is to avoid routine antibiotics and give meticulous supportive care. Antibiotics remain justified only for a clear separate indication, chosen carefully. [12]

3. Careful intravenous fluids to maintain renal perfusion; avoid nephrotoxins; transfuse for symptomatic anaemia; treat hypertension and fluid overload; refer early to nephrology and arrange renal replacement therapy for severe uraemia or fluid overload. Monitor full blood count, film, platelets, creatinine, electrolytes and blood pressure through the 5-10 day window and beyond, with long-term renal and cardiovascular follow-up because of late sequelae. [12]