In enteric fever caused by Salmonella typhi, the best method to isolate the organism in the FIRST week of illness is:
- A Stool culture
- B Urine culture
- C Blood culture ✓
- D Bone marrow culture
Explanation
Blood culture is the gold standard for diagnosing enteric fever in the first week of illness (positive in ~80% of cases), as S. typhi is primarily a bacteremic illness before localizing to the gut. From week 2 onward, stool and urine cultures become positive (Salmonella is excreted through bile into the intestine). Bone marrow culture is the most sensitive (90-95% positive) throughout the illness, even after antibiotic treatment, because macrophages in the marrow harbor the organisms, but it is invasive and rarely used. The Widal test becomes useful from the second week.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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