Leptospira interrogans

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Classification

Higher order taxa

Bacteria; Spirochaetes; Spirochaetes; Spirochaetales; Leptospiraceae; Leptospira

Species

NCBI: Taxonomy

Leptospira interrogans

Description and significance

Leptospira interrogans is a gram negative obligate aerobe. This bacterium is motile and has a spiral or helical shape like other spirochetes (1). It has an optimum temperature of 30 degrees Celsius and an optimum pH of 7.4. L. interrogans has a variety of hosts and occurs in many different regions. This bacterium causes leptospirosis which occurs mostly in wild animals. Rodents are one of the main hosts of this bacterium, but it can infect domestic animals and even humans usually causing a mild case (2). Species of Leptospira are divided into more than 200 serotypes based on the composition of their antigens (2).

Genome structure

L. interrogans is divided into many different serotypes, but two of them have their genome completely sequenced. L. interrogans serovar Lai str. 56601 is one of the serotypes. It has two chromosomes both of which are circular. Chromosome one of this serovar has a length of 4.3 Mbp and the second has a length of .36 Mbp. L. interrogans serovar Copenhageni str. Fiocruz L1-130 is the other serotype that has been sequenced. It also has two circular chromosomes. The first chromosome having a length of .2 Mbp and the second chromosome has a length of .35 Mbp (3,4,5,6,).

Cell structure and metabolism

Leptospira interrogans is an obligate aerobe so oxygen is its only terminal electron acceptor. The outermost layer is its outer sheath (7). Inside the outer sheath, there is a layer of peptidoglycan followed by the cytoplasmic membrane. L. interrogans has two periplasmic flagella, one on both ends between the peptidoglycan layer and the outer sheath. This bacterium needs fatty acids and several B vitamins to survive (2). L. interrogans is a chemoheterotroph and uses long-chain fatty acids as both its carbon and energy source (1).

Ecology

L. interrogans is mainly found in tropical regions but can also infect people and animals in temperate regions (7). The cells of the bacteria are at first found in the blood but after the first couple of week are found in several organs and can be expelled from the body in the urine. The bacteria can survive in urine infected soil for up to two weeks if the conditions are right. L. interrogans infects a variety of hosts, but usually infects wild animals. The usual reservoir is rodents. Domestic animals can also be reservoirs which is one of the sources of human infection (2).

Pathology

L. interrogans causes leptospirosis. The bacteria can enter the body through scratches or breaks in the skin. The bacteria use blood as a means of travel, traveling throughout the body and infecting different organs (2). It is believed that the bacteria can attach to several different receptors on the host cells which is why it can effect so many different hosts and attack different organs (7). The kidney is where L. interrogans survive and multiply the best, causing kidney infections. Having leptospirosis is usually not fatal to humans but has been known to cause death in a human at least once. There are two phases an animal goes through when being infected by L. interrogans, the leptosipremic acute phase and the immune leptospirosis phase. The symptoms during the first phase include fever, nausea, headaches, and muscle pain (2). An organism experiencing the second phase also will have fever and may develop meningitis. Organ failure and renal failure may occur in severe cases. It is during this phase that the bacteria leave the body through the urine (2)

Current Research

Current research is trying to determine out the virulence factors of L. interrogans as well as other species of Leptospira. Also, in the same study the researchers were looking at different genes in species of Leptospira to see how the genes differ between species and to see if there is a large difference between the pathogenic and non-pathogenic species of Leptospira (8). Researchers are often trying to test different regions to see if pathogens, including Leptospira interrogans, are present. One of the most recent studies done, tested different animals in Madagascar to see if they were infected with L. interrogans. They tested 268 small mammals, mostly rats and mice, and found that many of these animals were infected with L. interrogans. The researchers concluded that, contrary to other studies done in Madagascar, Leptospira interrogans is widespread in small mammals in Madagascar (9).

References

1 Krieg, Noel R., John G. Holt, and D. H. Bergey. Bergey's Manual of Systematic Bacteriology. Vol. 1. Baltimore: Williams & Wilkins, 1984. Print.

2 Johnson, Russell C. "Leptospira." Medical Microbiology. Ed. Baron S. 4th ed. Galveston, Texas: University of Texas Medical Branch at Galveston, 1996. Pubmed. Web. 13 Apr. 2011. http://www.ncbi.nlm.nih.gov/books/NBK8451/

3 "Leptospira Interrogans Serovar Copenhageni Str. Fiocruz L1-130 Chromosome Chromosome I, Complete Sequence." Genome. Web. http://www.ncbi.nlm.nih.gov/genome?Db=genome&Cmd=ShowDetailView&TermToSearch=396

4 "Leptospira Interrogans Serovar Copenhageni Str. Fiocruz L1-130 Chromosome Chromosome II, Complete Sequence." Genome. Web. http://www.ncbi.nlm.nih.gov/genome?Db=genome&Cmd=ShowDetailView&TermToSearch=397

5 “Leptospira interrogans serovar Lai str. 56601 chromosome chromosome I, complete sequence.” Genome. Web. http://www.ncbi.nlm.nih.gov/genome?Db=genome&Cmd=ShowDetailView&TermToSearch=258

6 “Leptospira interrogans serovar Lai str. 56601 chromosome chromosome II, complete sequence.” Genome. Web. http://www.ncbi.nlm.nih.gov/genome?Db=genome&Cmd=ShowDetailView&TermToSearch=259

7 Martinez-Lopez, Denise G., Mark Fahey, and Jenifer Coburn. "Responses of Human Endothelial Cells to Pathogenic and Non-Pathogenic Leptospira Species." PLoS Neglected Tropical Diseases (2010). Pubmed. Web. 14 Apr. 2011. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3001904/?tool=pubmed

8 Alder, Ben., Miranda Lo, and Torsten Seemann. “Pathogenesis of leptospirosis: The influence of genomics” Veterinary Microbiology (2011). Pubmed. Web. 15 Apr. 2011. http://www.ncbi.nlm.nih.gov/pubmed/21440384

9 Rahelinirina, Soanandrasana., Albertine Léon, and Rudy A. Harstskeerl. “First isolation and direct evidence for the existence of large small-mammal reservoirs of Leptospira sp. in Madagascar.” PLoS One (2010) Pubmed. Web. 25 Apr. 2011. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2991340/?tool=pubmed