Leptospira
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 Scanning electron micrograph of Leptospira interrogans.
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L. alexanderi |
Leptospira is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species.[1] The first Leptospira to be described was L. interrogans in 1907 (as Spirochaeta interrogans) was isolated from kidney tissue slices of a Leptospirosis victim. Before genotypic methods such as DNA-DNA hyrbidisation and 16s rRNA gene sequencing, Leptospira were divided into either pathogenic species - L. interrogans sensu lato or saprophytic species - L. biflexa sensu lato using phenotypic tests such as growth at 13 °C or 30 °C and growth in the presence of 8-azaguanine.
The genus is now divided into 17 genomospecies using DNA-DNA hybridisation (Brenner 1999, Levett 2006, Perolat 1998, Yasuda 1987):-
Known pathogenic Leptospira
- Leptospira interrogans
- Leptospira kirschneri
- Leptospira noguchii
- Leptospira alexanderi
- Leptospira weilii
- Leptospira genomospecies 1,
- Leptospira borgpetersenii
- Leptospira santarosai
Intermediates or opportunistic Leptospira
- Leptospira inadai
- Leptospira fainei
- Leptospira broomi
Non-pathogenic Leptospira
- Leptospira biflexa
- Leptospira meyeri
- Leptospira wolbachii
- Leptospira genomospecies 3
- Leptospira genomospecies 4
- Leptospira genomospecies 5
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[edit] Nomenclature
Leptospira is placed in the family Leptospiraceae, together with the genus Leptonema.
At its 2002 meeting, the Committee on the Taxonomy of Leptospira of the International Union of Microbiological Societies approved the following nomenclature for serovars of Leptospira. Genus and species must of course be italicized, with the serovar name not italicized and with an upper case first letter. International Leptospirosis Society Website
- Genus species serovar Serovar_name
- Genus and species italicised, serovar name in plain text, genus and serovar capitalised and species lowercase.
- Examples include:
- Leptospira interrogans serovar Australis strain Ballico
- Leptospira biflexa serovar Patoc strain Patoc 1
[edit] Description
The Leptospira are an extremaly varied (over 200 serovars known) group of helix-shaped motile gram-negative bacteria; if straightened, they'd measure 6-20 μm long and 0.1-0.15 μm in diameter. The number of curls depends on the straightened length and varies by as many as 20.[2]
The bacteria have a number of freedom degrees; when ready to proliferate via binary fission, the bacterium noticeably bends in the place of the future split.
Pathogenic leptospira have hook-like ends and extensively use axial flagella (one on each end) for penetration into host organism tissue; human infection may occur through even slightly damaged skin, mucouse membranes or eyes.
Leptospira, both pathogenic and saprotrophic, can occupy diverse environments, habitats and life cycles; it generally recognized these bacteria are virtually ubiquitous in terms of geographic distribution (present everywhere except Antarctica).[3]
Most of Leptospira, however, are hydrophilic - high humidity and neutral (6.9-7.4) pH are essential for their survival in the environment, with stagnant water reservoirs - bogs, shallow lakes, ponds, puddles, etc - being natural placeholder for the bacteria. Proliferation rate is typically slow; growth in an artificial nutrient environment (for L. interrogans, one typically contains human blood serum) becomes noticeable in around 5-7 days. Parasitic species' optimal growth temperature is 28-32 °C, while saprotrophic one can grow at as low as 13 °C.
Due to high variance of the pathogens, Leptospira-caused diseases leave immunity only to a particular serovar that actually caused the infection. This circumstance prevents creation of effective vaccines against leptospirosis.
[edit] See also
[edit] References
- ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0-8385-8529-9.
- ^ Johnson RC (1996). Leptospira. In: Barron's Medical Microbiology (Barron S et al, eds.), 4th ed., Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
- ^ Madigan M; Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0-13-144329-1.
