Bacterium
Leptospira interrogans
Question-mark spirochete; rat-urine water exposure
lep-toh-SPY-ruh in-TER-oh-ganz
High-yield clue
A tightly coiled spirochete with hooked ('question-mark') ends acquired from freshwater contaminated by animal urine; severe form is Weil disease with jaundice and kidney involvement.
Overview
A thin, tightly coiled aerobic spirochete with hooked ends that causes leptospirosis, a waterborne zoonosis. It is the classic teaching link between freshwater exposure to animal urine and Weil disease.
Classification
- Spirochete
- Tightly coiled with hooked ends
- Obligate aerobe
- Thin and motile (endoflagella)
Lab & identification clues
- Dark-field microscopy vocabulary
- Hooked / question-mark ends
- Serologic (agglutination) testing concept
- Very thin spirochete
Associations
- Freshwater / animal-urine exposure (zoonosis)
- Weil disease with jaundice and renal involvement
- Occupational and recreational water exposure
Commonly confused with
- Borrelia burgdorferi
- Treponema pallidum
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.