——————————————————— Spirochetes ——————————————————— >Leptospira species (includes pathogenic and saprophytic species) >Borrelia species (36 known strains). Most common strains associated with Lyme disease: 1] Borrelia burgdorferi 2] Borrelia afzelii 3] Borrelia garinii >Treponema pallidum
Although over 200 serotypes of Leptospira have been described, all members of the genus have similar morphology.
Leptospira are spiral-shaped bacteria that are 6-20 µm long and 0.1 µm in diameter
Because they are so thin, live Leptospira are best observed by darkfield microscopy.
Leptospira have a Gram-negative-like cell envelope consisting of a cytoplasmic and outer membrane. However, the peptidoglycan layer is associated with the cytoplasmic rather than the outer membrane, an arrangement that is unique to spirochetes.
The outer membrane of Leptospira, like those of most other Gram-negative bacteria, contains lipopolysaccharide (LPS). Differences in the highly immunogenic LPS structure account for the numerous serovars of Leptospira.
Important considerations: The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions. Generally, the most common agents/regimens are listed first.