Leptospirosis diagnosis: In the first week of illness (leptospiraemic phase), the most reliable laboratory method to isolate the organism is:

• A Blood culture in EMJH medium ✓
• B Darkfield microscopy of urine
• C Microscopic agglutination test (MAT) on acute-phase serum
• D IgM ELISA on urine

Explanation

During the leptospiraemic phase (days 1–7), leptospires are present in blood and CSF. Blood culture in EMJH (Ellinghausen-McCullough-Johnson-Harris) semisolid medium is the definitive isolation method — colonies are visible as 'Dinger-like rings' at 13–15 cm depth after incubation at 29°C for up to 4–6 weeks. MAT (microscopic agglutination test) is the gold standard serological test but antibodies appear in the second (immune) phase, so MAT is negative early. Darkfield microscopy of urine is performed later (week 2+) when leptospires appear in urine.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.