[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Spirochetes](https://durgical.com/en/microbiology/groups/spirochetes/) › Leptospira interrogans [Microbiology](https://durgical.com/en/microbiology/) · [Spirochetes](https://durgical.com/en/microbiology/groups/spirochetes/) # Leptospira interrogans - Bacterium - Does not Gram-stain - Exam priority: high A spirochete from the urine of rats and other animals; caught from water or mud, especially after floods, it can harm kidneys and liver. Updated 2026-11-01 ## Key points - Flood + fever + calf pain + red eyes without discharge = leptospirosis - Weil syndrome: jaundice + kidney failure + bleeding - Pulmonary haemorrhage is the deadliest form - MAT is the reference serological test ## At a glance **Gram** Does not Gram-stain **Shape** Thin spirochete with hooked ends **Oxygen** Aerobe **Family** Leptospiraceae **Stain** Stains poorly with Gram; dark-field or silver stain ## Morphology - Tightly coiled spiral with one or both ends shaped like a question mark - Highly motile thanks to endoflagella - Grows slowly in special media (EMJH) ## Transmission - Contact of broken skin or mucosa with water, mud or soil contaminated by animal urine - Direct contact with urine or tissues of infected animals (farm, veterinary, sewer work) - Outbreaks after heavy rain and floods; almost never person-to-person **Reservoir:** Rats and other rodents; Dogs, pigs, cattle and wild animals ### Isolation precautions What the care team adds to standard precautions. - Standard ## Virulence factors - Penetrates the skin and spreads rapidly through the blood (leptospiraemia) - Capillary endothelial damage: bleeding, vasculitis and kidney and liver injury - Colonises renal tubules and is shed in urine ## Diseases it causes - Leptospirosis: from mild febrile illness to severe forms [Leptospirosis →](https://durgical.com/en/conditions/leptospirosis/) - Acute kidney injury in Weil syndrome [Acute kidney injury →](https://durgical.com/en/conditions/acute-kidney-injury/) - Pulmonary haemorrhage syndrome and aseptic meningitis ## Clinical picture - Early phase: sudden fever, headache, severe calf myalgia and conjunctival suffusion - Immune phase: fever may return with meningitis or uveitis - Weil syndrome: jaundice, kidney failure and bleeding - Mimics dengue, malaria and hepatitis in the tropics ## Diagnosis - Microscopic agglutination test (MAT): serological reference, with paired samples - IgM ELISA from the first week - PCR on blood in the first days; on urine later - Lab clues: raised CK, low platelets, high creatinine and bilirubin ## Treatment Early antibiotics: doxycycline or amoxicillin for mild disease; intravenous penicillin or ceftriaxone for severe disease, with renal and respiratory support. A Jarisch-Herxheimer reaction may occur. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/) - [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/) - [Benzylpenicillin (penicillin G)](https://durgical.com/en/pharmacology/benzylpenicillin/) - [Ceftriaxone](https://durgical.com/en/pharmacology/ceftriaxone/) ## Prevention - Rodent control and waste management - Waterproof boots, gloves and clothing when working in water or mud; cover wounds - Doxycycline chemoprophylaxis for high-risk exposures, per health authorities - Vaccination of dogs and livestock **Vaccine:** There is no human vaccine in the PAI schedule; veterinary vaccines exist. ## In Colombia Endemic in Colombia, with peaks after rainy seasons and floods, especially in warm areas such as Antioquia, Valle del Cauca, the Caribbean coast and Tolima. It is a SIVIGILA (INS) notifiable event and is worked up alongside dengue and malaria in acute febrile illness. ## Memory aid «After the downpour, the rat sends the bill»: floodwater carries its urine, the bacterium enters through the skin and collects in the kidney, the liver and the eyes. ## Test yourself Think of the answer, then tap the question to see it. ## What is the classic urban reservoir of Leptospira? Rats, which shed the bacterium in urine for a long time. ## Which triad defines Weil syndrome? Jaundice, acute kidney injury and bleeding. ## Which eye sign suggests leptospirosis in a febrile patient? Conjunctival suffusion: red eyes without purulent discharge. ## What is the reference serological test for leptospirosis? The microscopic agglutination test (MAT), ideally with paired samples. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/leptospira-interrogans/) ## Related - [Treponema pallidum](https://durgical.com/en/microbiology/treponema-pallidum/) - [Borrelia recurrentis and tick-borne relapsing fever borreliae](https://durgical.com/en/microbiology/borrelia-recurrentis-and-tick-borne-relapsing-fever-borreliae/) ## Related conditions - [Leptospirosis](https://durgical.com/en/conditions/leptospirosis/) - [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. [← Back to the group: Spirochetes](https://durgical.com/en/microbiology/groups/spirochetes/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [About Leptospirosis | Leptospirosis | CDC](https://www.cdc.gov/leptospirosis/about/index.html) (Centers for Disease Control and Prevention (CDC), 2024); [Leptospirosis - PAHO/WHO | Pan American Health Organization](https://www.paho.org/en/topics/leptospirosis) (Pan American Health Organization (PAHO), 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/leptospira-interrogans/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/leptospira-interrogans/