Lyme disease microbiology

Lyme disease, or borreliosis, is caused by spirochetal bacteria from the genus Borrelia, which has 52 known species. Three main species (Borrelia garinii, Borrelia afzelii, and Borrelia burgdorferi s.s.) are the main causative agents of the disease in humans, while a number of others have been implicated as possibly pathogenic.Borrelia species known to cause Lyme disease are collectively called Borrelia burgdorferi sensu lato (s.l.).

Borrelia are microaerophilic and slow-growing—the primary reason for the long delays when diagnosing Lyme disease—and have been found to have greater strain diversity than previously estimated. The strains differ in clinical symptoms and/or presentation as well as geographic distribution.

Except for Borrelia recurrentis (which causes louse-borne relapsing fever and is transmitted by the human body louse), all known species are believed to be transmitted by ticks.

Until recently, only three genospecies were thought to cause Lyme disease (borreliosis): B. burgdorferi s.s. (the predominant species in North America, but also present in Europe); B. afzelii; and B. garinii (both predominant in Eurasia).

Thirteen distinct genomic classifications of Lyme disease bacteria have been identified worldwide. These include but are not limited to B. burgdorferi s.s., B. afzelii, B. garinii, B. valaisana, B. Lusitaniae, B. andersoni, 25015, DN127, CA55, 25015, HK501, B. Miyamotoi, and B. Japonica. Many of these genomic groups are country or continent specific. For example, without migration, B. Japonica is only prevalent in the eastern hemisphere.

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