Leptospirosis is best diagnosed by which method in the second week of illness when leptospires have cleared from the blood?

• A Blood culture in EMJH medium
• B Darkfield microscopy of whole blood
• C PCR of urine for Leptospira DNA
• D Microscopic agglutination test (MAT) detecting serum antibodies ✓

Explanation

During the first week of leptospirosis (leptospiraemic phase), organisms are detectable in blood and CSF by culture/PCR. From the second week onwards, leptospires disappear from blood as antibodies rise and organisms concentrate in urine (leptospiruric phase). The microscopic agglutination test (MAT) using live or formalin-killed Leptospira serovars is the reference standard serological test; a fourfold rise in paired sera or a single titer ≥1:800 in an endemic area is diagnostic. MAT also identifies the infecting serogroup. Urine PCR is useful in the second week, while blood culture sensitivity is highest in week 1.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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