Enteric fever — DTM&H MCQ

Correct answer: E — Blood culture

The correct answer is E, blood culture, because it remains the reference investigation for diagnosing enteric fever (typhoid or paratyphoid) in a returning traveller with stepwise fever, abdominal discomfort and relative bradycardia. The organism described, a motile Gram negative bacillus growing from blood, is entirely consistent with Salmonella Typhi or Paratyphi, and blood culture confirms this while allowing sensitivity testing, essential given high fluoroquinolone resistance in isolates from Pakistan. UK guidance from the British Infection Association, developed with UKHSA and the Hospital for Tropical Diseases, London, recommends blood culture as the key diagnostic test, ideally before starting antibiotics. Repeated cultures increase yield since bacteraemia can be intermittent, and culture also permits susceptibility testing to guide safe empirical therapy. Why the other options are wrong: A. Dengue IgG: Dengue is viral and does not grow on blood culture; a positive Gram negative bacillus isolate already excludes this diagnosis. D. Skin snip microscopy: This detects microfilariae in onchocerciasis, a filarial infection unrelated to bacteraemic febrile illness. C. Urine ova microscopy: This detects schistosome eggs in urinary schistosomiasis, which does not cause bacteraemia or a positive blood culture. B. Widal test as sole test: It has poor sensitivity and specificity, cross reacts with other Enterobacteriaceae, and cannot substitute for culture and susceptibility data once an organism has already been isolated. Key point: In a febrile returning traveller with a Gram negative bacillus bacteraemia, blood culture with sensitivities is both diagnostic and essential for safe antibiotic selection given widespread fluoroquinolone resistance in South Asian isolates.

Reference: British Infection Association / UKHSA. Guidelines for the diagnosis, management, prevention and control of enteric fever in England, 2022. https://www.britishinfection.org/application/files/6816/5461/2016/EFpublished__guidance_13042022.pdf