Rickettsia prowazekii has a transport mechanism that exchanges ATP for ADP in its intracellular environment, thus providing a means to usurp host cell energy sources under favorable circumstances. Rickettsiae also are able to synthesize ATP via metabolism of glutamate.
What is Rickettsia rickettsii?
Rickettsia rickettsii is a small, rod-shaped bacterium known to cause Rocky Mountain spotted fever (RMSF). This disease can be transmitted to humans either from a tick bite with an incubation period of 1 week, or by contamination of a cut on the skin or a wound with ticks feces.
How is Rickettsia transmitted from human to human?
Rickettsiae are transmitted to humans by the bite of infected ticks and mites and by the feces of infected lice and fleas. They enter via the skin and spread through the bloodstream to infect vascular endothelium in the skin, brain, lungs, heart, kidneys, liver, gastrointestinal tract, and other organs (Fig. 38-1).
How do Rickettsia infect smooth muscle?
From the portal of entry in the skin, rickettsiae spread via the bloodstream to infect the endothelium and sometimes the vascular smooth muscle cells. Rickettsiaspecies enter their target cells, multiply by binary fission in the cytosol, and damage heavily parasitized cells directly.
See more
Can Rickettsia produce ATP?
Despite generating ATP via Glu oxidation, Rickettsia species were shown to possess an ATP/ADP symporter, termed nucleotide translocase (Tlc1), which exchanges host ATP for bacterial ADP without a change in the total adenylate pool (38).
How does Rickettsia grow and reproduce?
Rickettsia replicates through binary fission and invades the nearby cells by inducing filopodia formation. Via filopodia propulsion, the rickettsiae are either released extracellularly or spread into the adjacent cell (Walker and Ismail 2008).
Is Rickettsia aerobic or anaerobic?
Introduction to the Rickettsiae The Rickettsiae are small (0.3-0.5 x 0.8-2.0 um), Gram-negative, aerobic, coccobacilli that are obligate intracellular parasites of eucaryotic cells. They may reside in the cytoplasm or within the nucleus of the cell that they invade.
How does Rickettsia grow?
Growth and Plaquing Characteristics. Rickettsia are obligate intracellular bacteria that are unable to grow axenically. Rickettsia can be cultivated in the yolk sacs of embryonated chicken eggs. The optimal growth temperature for SFG rickettsiae is 32–34°C.
How does Rickettsia survive?
As an obligate intracellular pathogen, rickettsial survival is dependent upon entry into, growth, and replication within the eukaryotic host cell cytoplasm and then exit to initiate a new infection cycle (1). Generally, the outcome of infection is the host cell lysis and the release of rickettsial progeny.
Is Rickettsia related to mitochondria?
The genus Rickettsia and mitochondria are closely related groups of descent ([16] and Fig. 2) and as such share some traits derived from CA. In particular, both R.
How does Rickettsia Rickettsii move around?
rickettsii organisms move through the cell cytoplasm at an average rate of 4.8 ± 0.6 μm/min (mean ± standard deviation). This speed was 2.5 times slower than that of L. monocytogenes, which moved at an average rate of 12.0 ± 3.1 μm/min.
What is the characteristics of Rickettsia?
The rickettsiae are rod-shaped or variably spherical, nonfilterable bacteria, and most species are gram-negative. They are natural parasites of certain arthropods (notably lice, fleas, mites, and ticks) and can cause serious diseases—usually characterized by acute self-limiting fevers—in humans and other animals.
What transmits Rickettsia Rickettsii?
TRANSMISSION. Most rickettsial organisms are transmitted by the bites or infectious fluids (such as feces) inoculated into the skins from ectoparasites such as fleas, lice, mites, and ticks. Inhaling bacteria or inoculating conjunctiva with infectious material may also result in infection.
What is the habitat for Rickettsia?
Habitat in the Host Cell- Rickettsia rickettsii is a parasite of eukaryotic cells and needs two hosts, normally an arthropod vector (American dog tick and Rocky Mountain wood tick) and a mammal host (any mammalian can pick up the bacterium Rickettsia rickettsii).
Can Rickettsia live outside the host?
Rickettsiae live in small insects such as ticks, fleas, mites, and lice and can infect mammals (including humans), but cannot survive for any significant period outside their host.
Where does Rickettsia multiply?
In their arthropod vectors, the rickettsia multiply in the epithelium of the intestinal tract; they are excreted in the feces, but occasionally gain access to the arthropods salivary glands. They are transmitted to man, via the arthropod saliva, through a bite.
Where does Rickettsia multiply?
In their arthropod vectors, the rickettsia multiply in the epithelium of the intestinal tract; they are excreted in the feces, but occasionally gain access to the arthropods salivary glands. They are transmitted to man, via the arthropod saliva, through a bite.
How is Rickettsia spread?
Most rickettsial organisms are transmitted by the bites or infectious fluids (such as feces) inoculated into the skins from ectoparasites such as fleas, lice, mites, and ticks. Inhaling bacteria or inoculating conjunctiva with infectious material may also result in infection.
What culture media does Rickettsia grow in?
Accordingly, Rickettsia species cannot grow in artificial nutrient culture; they must be grown either in tissue or embryo cultures; typically, chicken embryos are used, following a method developed by Ernest William Goodpasture and his colleagues at Vanderbilt University in the early 1930s.
What is the habitat for Rickettsia?
Habitat in the Host Cell- Rickettsia rickettsii is a parasite of eukaryotic cells and needs two hosts, normally an arthropod vector (American dog tick and Rocky Mountain wood tick) and a mammal host (any mammalian can pick up the bacterium Rickettsia rickettsii).
What is the effect of Rickettsia rickettsii infection?
There is an increase in the secretion of cytokines and proteins. During Rickettsia rickettsii infection, nuclear factor-kappa B (NF-KB) is activated. This is a group of transcription factors that regulate cell adhesion, proliferation, the immune system, inflammation, stress responses, and host pathogenic interactions. [10]
Where is Rickettsia rickettsii transmitted?
In North America, it’s more well known in the southeast and southcentral states. In North America, Rickettsia rickettsii is transmitted by the American dog tick ( Dermacentor variabilis) and the Rocky Mountain wood tick ( Dermacentor andersoni ). In Latin America, Rickettsia rickettsii is transmitted by Rhipicephalus sanguineus and ...
What would happen if ticks shared meals with each other?
In addition, if the ticks shared meals with each other, the rate of rickettsial infection would increase. Furthermore, Rickettsia rickettsii transmission from the parent tick into the offspring tick also increases the rickettsial infection rate.
Why is Rickettsia rickettsii a priority pathogen?
The Centers for Disease Control and Prevention (CDC) has classified Rickettsia rickettsii as a Category C priority pathogen due to the fact that the organism can be used as a bioterroism agent. In addition, dogs could serve as the foundation of bioterrorist attacks using Rickettsia rickettsii.
How long does it take for a tick to spread a rmsf?
This disease can be transmitted to humans either from a tick bite with an incubation period of 1 week, or by contamination of a cut on the skin or a wound with ticks feces. Dr.
Why is it so hard to detect RMSF?
Doctors have a hard time detecting RMSF because the patients rarely have the Rickettsia rickettsii antibodies. Although PCR (Polymerase Chain Reaction) testing is available in a few laboratories, detection of Rickettsial DNA in the blood is still lacking, especially in the early symptoms.
How many genes are in Rickettsia rickettsii?
The unfinished genome sequencing of Rickettsia rickettsii is made up of 1,257,710 nucleotides. There are 1311 genes, and all of them code for proteins. The guanine and cytosine content is 32% of its DNA. Rickettsia rickettsii has no pseudo genes, and it’s made up of DNA molecules.
How do Rickettsiae attach to their host cell?
R. rickettsii attaches to its host cell by using a major rickettsial outer membrane protein (rompA), 3 and subsequently is endocytosed by the host endothelial cell.
How does R. rickettsii spread?
R. rickettsii attaches to its host cell by using a major rickettsial outer membrane protein (rompA), 3 and subsequently is endocytosed by the host endothelial cell. Intracellular movement of R. rickettsii and spread to adjacent endothelium involves rickettsia-mediated polymerization of host-cell actin. Oxidative injury to host cells leads to diffuse microvascular injury and fluid leakage into extravascular spaces. 4–8
What is the etiologic agent of Rocky Mountain spotted fever?
Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever (RMSF), is a small, obligately intracellular, gram-negative, rod-shaped organism that is among the most pathogenic of all known bacteria. Although R. rickettsii can infect several different cell types, its primary targets in mammalian hosts are the endothelial cells lining capillaries, arterioles, and venules of all major tissues and organ systems ( Fig. 178.1 ). 1 Damage to endothelium of the dermis, skeletal muscle, and vital organs such as brain, heart, lungs, kidneys, and gastrointestinal tract results in the systemic manifestations characteristically observed in people with RMSF.
What ticks are in the Rocky Mountain region?
Rocky Mountain Spotted Fever. Rickettsia rickettsii is transmitted by the wood tick, Dermacentor andersoni, in the Rocky Mountain region and by the dog tick, Dermacentor variabilis, in the eastern United States. Mild to moderate transaminase elevations and occasionally jaundice may be seen. The main pathologic lesion is vasculitis, ...
What are the targets of RMSF?
The primary targets are the endothelial cells of small blood vessels of all major tissues and organs. This accounts for the protean manifestations of RMSF, including the rash, and the significant morbidity and mortality of the illness. The incidence of RMSF is approximately 3.5 cases per million population.
What are the obligate intracellular bacterial parasites transmitted by ticks?
Rickettsias such as Rickettsia rickettsii, Ehrlichia equi and Ehrlichia chaffeensis, and Orientia tsutsugamushi are obligate intracellular bacterial parasites transmitted by insects or ticks. These bacteria are the etiologic agents of Rocky Mountain spotted fever, ehrlichiosis, and scrub typhus, respectively, and may theoretically be transmitted by transfusion. However, there are no reports of adverse transfusion reactions in recipients who have received blood units from rickettsia-infected donors. 53,54 Similarly, recipients of blood components from donors subsequently diagnosed as having Lyme disease, which is caused by the tick-borne spirochete Borrelia burgdorferi, have not demonstrated any signs or symptoms of the disease. 55–61
Where is Rickettsia found?
Rickettsia rickettsii (Rocky Mountain spotted fever, found in Western continents, and not confined to the Rocky Mountains)
How is R. rickettsii transmitted?
In Arizona, R. rickettsii are mainly transmitted by the brown dog tick, infecting domestic and stray dogs which can then be passed on to people. More frequent cases of RMSF are found in men compared to women, as well as in native Americans compared to other groups.
How to prevent R. rickettsii?
The best way to prevent infection of R. rickettsii would be to prevent tick bites. Ticks can be found in wooded areas such as forests, campgrounds and even in some people’s backyards. Wearing clothing that protects skin from encountering brush or grass can help reduce tick bites.
How does RMSF spread?
RMSF is called this because it was first identified in the Rocky Mountain region and was found to produce red spots that can sometimes cover the whole body including the palms of hands and soles of feet. It is caused by R. rickettsii, transmitted to humans mainly through a tick as the vector. Ticks become infected by feeding off the blood of infected animals. The most common types of tick species that the bacteria are found in are the American dog tick, Rocky Mountain wood tick and the brown dog tick. Once a human, or mammal, is bitten by an infected tick, the tick needs to be attached to the host for 6-10 hours for R. rickettsii to be released from the tick’s salivary glands. Once transmitted into the host, it begins to live and multiply in endothelial cells of the body (Figure 1). Endothelial cells line the interior surface of blood vessels and lymphatic vessels. R. rickettsii can rapidly enter the cells and reduce the immune response of the host so that it can continue to cause infection without being eaten up by the host defensive cells, like macrophages, as quickly compared to having a full immune response. This process of immune system evasion increases its survival in the host and prolongs the time it takes for the digestive cells to take over and eat up the bacteria. The infection of these cells increases vascular permeability of the blood vessels, which can lead to several symptoms such as fever, muscle pain, nausea, vomiting and skin rashes amongst many others.
What is the cause of Rocky Mountain spotted fever?
Rickettsia rickettsii is the causative agent of Rocky Mountain spotted fever (RMSF). This bacterium is a gram-negative, intracellular bacterium most frequently found in hard-bodied ticks in the environment. If bitten by an infected tick, R. rickettsii can then infect the endothelial cells of mammals, including humans. It is the most lethal of all bacteria in the spotted fever group “ rickettsiae.”
What are the two proteins that help R. rickettsii attach to endothelial cells?
Virulence Factors. During bacterial endothelial infection, R. rickettsii first gets into endothelial cells using surface adhesion proteins, OmpA and OmpB, which help them quickly attach to and pass into endothelial cells, a process called endocytosis (Figure 2a).
What are the symptoms of Rickettsia rickettsii?
The infection of these cells increases vascular permeability of the blood vessels, which can lead to several symptoms such as fever, muscle pain, nausea, vomiting and skin rashes amongst many others. Figure 1: Microscopic image of Rickettsia rickettsii (red) found in blood vessel endothelial cells (blue/purple).
How long does it take for a tick to get out of the human body?
Once a human, or mammal, is bitten by an infected tick, the tick needs to be attached to the host for 6-10 hours for R. rickettsii to be released from the tick’s salivary glands.
How does R. rickettsia get into humans?
[4][5][6] Epidemiology. R. rickettsia transmits into human hosts by the bite of an infected tick. Humans are not a natural reservoir of disease.
How long does it take for a rickettsia to show up?
Patients typically present with symptoms four to ten days after exposure to the Rickettsia via tick bite. Patients may or may not recall the tick bite, as the tick does not need to have prolonged contact with the host to cause infection. A detailed travel history is important to identify any outdoor activities in endemic areas and areas with other endemic Rickettsia, as symptoms overlap between the various Rickettsial infections. Symptoms classically include the triad of fever, headache, and a petechial or maculopapular rash but may also include lymphadenopathy, central nervous system changes such as confusion or nuchal rigidity, myalgias and arthralgias, hepatitis, vomiting, and cardiovascular instability. The rash often begins as a maculopapular rash around the wrists and ankles that progresses to petechia. It is essential to have a high index of suspicion for rickettsial infection when patients present with these "influenza-like" symptoms during the summer months, regardless of known tick or insect exposure.
What causes Rocky Mountain spotted fever?
Rickettsia preferentially infects the vascular endothelial cells lining small and medium vessels throughout the body, causing the systemic symptoms and high mortality occurs with Rocky Mountain spotted fever. The infection of endothelial cells leads to disseminated inflammation, loss of barrier function, and altered vascular permeability throughout the body. This condition leads to fever, myalgias, central nervous system symptoms such as headache and confusion, rash, and cardiovascular instability that can be present in patients with Rocky Mountain spotted fever. The mechanisms involved in the rapid entry of the organisms into the cell and the downregulation of immune pathways allowing for persistence of infection are targets of studies to identify new therapeutic targets in these illnesses.
How long does it take for a spotted fever to go away?
The treatment course is usually seven to ten days , or for at least three days after defervescence. It is important to note than in severe rickettsial disease, such as Rocky Mountain spotted fever, mortality rates are as high as 20% to 30% without prompt antibiotic treatment. Thus, treatment should not delay while awaiting confirmatory laboratory testing in a patient with a suspected rickettsial infection; this is particularly important in children, who are at high risk of morbidity and mortality but may experience delays in treatment due to concerns with doxycycline use in children younger than age 8. The risk of dental staining in the treatment of Rocky Mountain spotted fever is very low, as dental staining is a cumulative dose effect, and treatment for Rocky Mountain spotted fever is typically seven to ten days. Thus, concerns regarding tooth staining should not delay treatment in suspected Rocky Mountain spotted fever. [11][12][13][14]
Can Rickettsia be transmitted?
Humans are not a natural reservoir of disease. The Rickettsia does not harm the tick. In the United States, transmission occurs most often after a bite of the American dog tick (Dermacentor variabilis), the Rocky Mountain wood tick (Dermacentor andersoni), or the brown dog tick (Rhipicephalus sanguineus).
How do Rickettsiae reproduce?
Virtually all rickettsiae can reproduce only within animal cells. Rickettsiae are usually transmitted to humans by a bite from an arthropod carrier. Because certain species can withstand considerable drying, transmission of rickettsia can also occur when arthropod feces are inhaled or enter the skin through abrasion.
Where do rickettsial infections occur?
The other rickettsial infections occur primarily in animals, which serve as reservoirs from which bloodsucking arthropods acquire the rickettsial bacteria and in turn transmit them to other animals and, occasionally, humans. Read More on This Topic. human disease: Rickettsial diseases.
What are the protective measures against rickettsiosis?
Protective measures against rickettsial disease agents include the control of arthropod carriers when necessary and immunization. Animals that recover from a rickettsiosis exhibit long-lasting immunity. Artificial immunity, as a preventive, is variably effective, typhus and the spotted fevers being among the easiest to immunize against. The most effective treatment of most rickettsioses includes the timely and prolonged administration of large amounts of broad-spectrum antibiotics such as tetracycline or, if tetracycline cannot be used, chloramphenicol.
What is the largest rickettsial genus?
The largest rickettsial genus, Rickettsia, is generally subdivided into the typhus group, the spotted fever group, and the scrub typhus group. This genus alone is responsible for a number of highly virulent diseases including Rocky Mountain spotted fever, epidemic typhus, Brill-Zinsser disease, scrub typhus, and others, as shown in the Table.
What is the size of a rickettsiae?
The rickettsiae range in size from roughly 0.3 to 0.5 micrometre ( μ m) by 0.8 to 2.0 μ m (1 μ m = 10 -6 metre).
What is the best treatment for rickettsiosis?
The most effective treatment of most rickettsioses includes the timely and prolonged administration of large amounts of broad-spectrum antibiotics such as tetracycline or, if tetracycline cannot be used, chloramphenicol. Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now.
Where does Rickettsia rickettsii live?
Rickettsia rickettsii reside in host cells and it takes two different hosts to complete its life cycle. However, there are a few states in which Rickettsia rickettsii are more common. Rickettsia rickettsii causes Rocky Mountain spotted fever which has been reported mainly in the south-Atlantic region of the United States. These states include: Delaware, Maryland , Washington D.C. , Virginia, West Virginia, North Carolina *, South Carolina, Georgia, and Florida . A few more cases were reported in the Pacific region ( Washington, Oregon, and California) and west south-central ( Arkansas, Louisiana , Oklahoma *, and Texas) region.
What is the habitat of Rickettsia rickettsii?
Habitat in the Host Cell- Rickettsia rickettsii is a parasite of eukaryotic cells and needs two hosts, normally an arthropod vector (American dog tick and Rocky Mountain wood tick) and a mammal host (any mammalian can pick up the bacterium Rickettsia rickettsii). When they invade the cells they normally reside in the cytoplasm or nucleus.
Classification
Description and Significance
- Rickettsia rickettsii is a small, rod-shaped bacterium known to cause Rocky Mountain spotted fever (RMSF). This disease can be transmitted to humans either from a tick bite with an incubation period of 1 week, or by contamination of a cut on the skin or a wound with ticks feces. Dr. Ricketts first isolated this microbe in Montana, 1906. Rickettsia need host cells to be able to …
Genome Structure
- The unfinished genome sequencing of Rickettsia rickettsii is made up of 1,257,710 nucleotides. There are 1311 genes, and all of them code for proteins. The guanine and cytosine content is 32% of its DNA. Rickettsia rickettsiihas no pseudo genes, and it’s made up of DNA molecules. In addition, no known plasmids have been found. Infection with Rickettsia rickettsii also triggers a…
Cell Structure and Metabolism
- The Rickettsia rickettsii bacteria are intracellular organisms, and they live in the cytoplasms of host cells sometimes in the nucleus. They are adapted as intracellular organisms because they have transport systems and metabolic enzymes. These microbes take about 8 hours to undergo binary fission. Rickettsia rickettsiiundergo aerobic oxidation, an...
Ecology
- Rickettsia rickettsii can be found in the western hemisphere, more notably in North America and South America. In North America, it’s more well known in the southeast and southcentral states. In North America, Rickettsia rickettsii is transmitted by the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni). In Latin America, Rickett…
Pathology
- Typical symptoms of RMSF can appear 2 to 14 days after exposure and include fever, headache, depression, nausea, vomiting, and gradually may develop a skin rash called purpura or petechiae. Sometimes the rash occurs 2 to 5 days after the onset of the fever. Serious cases of RMSF can include central nervous system, pulmonary, or hepatic injuries. Patients that have compromised …
Application to Biotechnology
- The organism Rickettsia rickettsiihas no significant contribution in forming compounds or enzymes related to biotechnology. However, it can be used as a form of a bioterrorism agent, especially using dogs to spread the infection of Rocky Mountain Spotted Fever.
Current Research
- Currently there is a major lack in controlling the RMSF organism. In addition, an effective diagnostic test to detect early symptoms is still not available. Doctors have a hard time detecting RMSF because the patients rarely have the Rickettsia rickettsiiantibodies. Although PCR (Polymerase Chain Reaction) testing is available in a few laboratories, detection of Rickettsial D…
References
- 1) NCBI Taxonomy Browser "Rickettsia rickettsii"Retrieved 26 August, 2007. 2) Whitney, Jamie MD. "Rocky Mountain Spotted Fever". Primary Care Update for OB/GYNS. Volume 9. Issue 1. January-February 2002. Pages 28-32. 3) NCBI Genome "Rickettsia rickettsii"Retrieved 28 August, 2007. 4) Joshi, S., Kovács, A. "Rickettsia rickettsiiinfection causes apoptotic death of cultured ce…