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
Frequently asked questions
What is Leptospira interrogans?
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.
What are the lab clues for Leptospira interrogans?
Lab clues for Leptospira interrogans include Dark-field microscopy vocabulary, Hooked / question-mark ends, Serologic (agglutination) testing concept, and Very thin spirochete.
What is Leptospira interrogans commonly confused with?
Leptospira interrogans is commonly confused with Borrelia burgdorferi and Treponema pallidum.
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.