Leptospira

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Leptospira
SEM image of L. interrogans

SEM image of L. interrogans

Systematics
Domain : Bacteria (bacteria)
Department : Spirochaetae
Class : Spirochetes (spirochaetes)
Order : Spirochaetales
Family : Leptospiraceae
Genre : Leptospira
Scientific name
Leptospira
Noguchi emend in 1917. Faine & Stallman 1982

Leptospira is a genus of bacteria whose cells are helically wound. They arealsocalled" Germanized " leptospira . Sometypes of Leptospira can cause infectious diseases called leptospirosis .

features

Appearance

These are gram-negative , very thin (diameter approx. 0.1 µm), in the middle part helically wound bacterial cells . The length varies with the number of turns and is between 6 and 20 µm. The ends are hook-shaped or button-like thickened, which makes the cells of Leptospira resemble a clothes hanger or walking stick. Due to the slim shape of the cells, they can pass through the pores of membrane filters with a pore size of 0.2 µm or more. Membrane filters with such pore sizes are often used in microbiology to remove bacteria from a liquid, which Leptospira cannot do. The cells are actively mobile (motile). The movement is characterized by rotations around the body axis, resulting in helical back and forth movements. Endospores are not formed.

The cells grow into colonies on solid nutrient media ; in test tubes , these typically appear in the form of a flat disk 1–3 cm below the surface of the nutrient medium. In semi-solid nutrient media that contain less than 1% agar-agar , colonies are also formed below the surface. Due to the motility, their shape can be diffuse, i.e. without clear delimitation.

Growth and metabolism

Leptospira species are heterotrophic . The metabolism is obligatory aerobic , i. H. the representatives of the genus can only multiply if oxygen is present. They have the enzyme catalase or other peroxidases . Some species are microaerophilic . In the context of chemoorgano-heterotrophic metabolism, long-chain fatty acids are preferred as a source of carbon and energy. Inorganic ammonium salts are used as a nitrogen source , amino acids are not suitable for this.

Growth takes place at pH values of 6.8–7.8, optimal values ​​are pH 7.2–7.6. Leptospira species show growth in a temperature range of 13 to 40 ° C, the optimal temperature range is 28–30 ° C. The multiplication through cell division takes place only slowly, the generation time in the nutrient medium is between 7 and 16 hours, which is comparable to the generation time of Treponema pallidum , another member of the order of the Spirochaetales . In contrast, Escherichia coli , for example, has a generation time of only 20 minutes. Therefore, culture media inoculated with Leptospira must be incubated for a correspondingly long time, 6–14 days are usual, with some species four weeks or longer are necessary before colonies are recognizable.

Chemotaxonomic Features

The GC content (the proportion of the nucleobases guanine and cytosine ) in the DNA of Leptospira species is between 35.3 and 41.0 mol percent. The murein layer in the cell wall contains the diamino acid 2,6-diaminopimelic acid as a diagnostically important amino acid. As usual for gram-negative bacteria, an outer membrane is deposited on the cell wall. In the contained lipopolysaccharide is methyl - mannose as sugar building block of importance.

proof

The cultivation of Leptospira species is unproblematic, but requires special culture media. They often contain an addition of serum , serum albumin (for example bovine serum albumin) or long-chain fatty acids with at least 14 carbon atoms. As growth factors are thiamine (vitamin B 1 ), and cyanocobalamin (vitamin B 12 ) is necessary. The light microscopic examination of living leptospira with the common brightfield microscopy is not possible, instead darkfield microscopy or phase contrast microscopy is used. The technique of depositing colloidal silver is suitable for staining fixed cells .

Systematics

The genus Leptospira belongs to the family of the Leptospiraceae in the order of the Spirochaetales. The type species is Leptospira interrogans . The following types are known (as of 2014):

The species Leptospira alexanderi is in the first description by Don J. Brenner et al. (Engl. with five "genome species" genomospecies represented). These are species that were simply not named because only one bacterial strain or, in one case, two bacterial strains are known. The species name L. alexanderi was only specified for genome species 2 . Since the designation as genome species 1, 2 etc. had led to confusion, a subcommittee on the Taxonomy of Leptospiraceae was established by the International Commission for the Systematics of Prokaryotes , which in 2013 created new taxa has established. Thereafter, genome species 1 was classified as L. alstonii , 3 as L. vanthielii , 4 as L. terpstrae and 5 as L. yanagawae .

Several species are further divided into serogroups and serovars .

etymology

The generic name Leptospira refers to the appearance of the bacterial cells with "delicate coils". The Greek word leptos means “thin” or “delicate”, the Latin word spira stands for “twist”.

Occurrence and meaning

Leptospira species occur both parasitically ( L. interrogans ) in humans and animals, as well as in the wild ( L. biflexa ). The hosts often include rodents , but also dogs and pigs . L. interrogans is the most important pathogenic representative and causative agent of leptospirosis . L. biflexa , L. meyeri and L. wolbachii are non- pathogenic. Parasitic Leptospira species prefer to colonize the kidneys or liver of their host. They can be excreted through the kidneys in the urine , which is then often a source of infection .

Reporting requirement

In Germany, the direct or indirect detection of human pathogenic Leptospira ( human pathogenic Leptospira sp. ) Must be reported by name in accordance with Section 7 of the Infection Protection Act , provided the evidence indicates an acute infection.

In Austria, suspected cases, cases of illness and death from leptospiral diseases are notifiable in accordance with Section 1, Paragraph 1, Number 1 of the 1950 Epidemic Act . Doctors and laboratories, among others, are obliged to report this ( Section 3 Epidemics Act).

swell

literature

H.-J. Selbitz: Leptospira . In A. Rolle and A. Mayr (eds.): Medical microbiology, infection and epidemic theory . 7th edition. Enke, Stuttgart 2001, ISBN 3-432-84686-X .

Individual evidence

  1. ↑ a b c d e f g h i S. Faine, ND Stallmann: Amended Descriptions of the Genus Leptospira Noguchi 1917 and the Species L. interrogans (Stimson 1907) Wenyon 1926 and L. biflexa (Wolbach and Binger 1914) Noguchi 1918. In: International Journal of Systematic Bacteriology. Volume 32, No. 4, October 1982, pp. 461-463, ISSN  0020-7713 . doi : 10.1099 / 00207713-32-4-461 .
  2. ↑ a b c Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 3-8274-0566-1 , pp. 597-600.
  3. ^ A b c Jean Euzéby, Aidan C. Parte: Genus Leptospira. In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved April 9, 2014 .
  4. ↑ L. Smythe, B. Adler et al. a .: Classification of Leptospira genomospecies 1, 3, 4 and 5 as Leptospira alstonii sp. nov., Leptospira vanthielii sp. nov., Leptospira terpstrae sp. nov. and Leptospira yanagawae sp. nov., respectively. In: International journal of systematic and evolutionary microbiology. Volume 63, No. 5, May 2013, pp. 1859-1862, ISSN  1466-5034 . doi : 10.1099 / ijs.0.047324-0 . PMID 22984140 .
  5. ↑ TRBA (Technical Rules for Biological Agents) 466: Classification of prokaryotes (Bacteria and Archaea) into risk groups. In: Website of the Federal Institute for Occupational Safety and Health (BAuA). April 25, 2012, p. 119 , accessed April 9, 2014 .