Leptospires

Leptospires are a genus of slender, spiral-shaped bacteria in the family Leptospiraceae. They are Gram-negative, highly motile spirochetes with axial filaments that enable a characteristic corkscrew motion. They are slow-growing and require specialized media for culture.

The genus includes both pathogenic and saprophytic species. Pathogenic leptospires, such as Leptospira interrogans and related serovars, cause disease in humans and animals; saprophytic species are typically nonpathogenic and inhabit soil and water. They are distributed worldwide, with higher incidence in warm, wet environments.

Transmission occurs mainly through contact with urine or urine-contaminated water or soil from infected animals. Infection occurs when the organism penetrates abraded skin or mucous membranes; ingestion is less common. Rodents are common reservoirs; livestock and dogs can also harbor pathogens.

In humans, leptospirosis ranges from a self-limited febrile illness to severe disease with jaundice (Weil disease), renal failure, pulmonary hemorrhage, and meningitis. Incubation is typically 5–14 days. Biphasic illness is common: an acute septicemic phase followed by an immune phase.

Diagnosis relies on serology, especially the microscopic agglutination test (MAT), and molecular methods such as PCR in the early phase. Cultures require specialized media like EMJH and slow growth. Treatment uses antibiotics (doxycycline, penicillin or ceftriaxone); severe cases may require intravenous therapy. Prevention centers on avoiding exposure, rodent control, and vaccination of animals; human vaccines are limited.

The disease and organism were historically described in the late 19th century; the name Leptospira reflects their slender form.