A 34-year-old sewer worker admitted with fever, conjunctival suffusion and jaundice is now on day 12 of illness. Blood cultures drawn on admission were negative. He is improving with supportive care. At this stage of leptospirosis, the specimen with the highest yield for isolation of Leptospira is:

• A Blood
• B Cerebrospinal fluid
• C Bone marrow
• D Urine ✓

Explanation

Leptospirosis is biphasic. In the first leptospiraemic week the organism circulates in blood and CSF, so blood or CSF culture yields the organism. From the second week onwards, agglutinating antibodies clear the blood and the organism localises in renal tubules, being shed in urine for up to a month. Therefore in the immune phase, urine is the specimen of choice for culture or dark-field examination. Bone marrow is never used for leptospiral isolation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.