Rickettsia-Presentation.ppt

Rickettsia The supervisors: Mr. Abed Elkader Elottol Collected by: Ahmad al-Aswad

Content Name of the pathogen General characteristics Virulence factors Diseases Cultural characters Sample collection world distribution Vaccine

Discovery Classification Pathogenicity transmission routes Weil-Felix test Identification Treatment References

Name of the pathogen the order Rickettsiales consists of three families: 1. Rickettsiaceae (genera Rickettsia, Coxiella, Rochalima,and Orientia) 2. Ehrlichiaceae (Ehrlichia, Anaplasma, Neorickettsia) 3. Bartonellaceae (genera Bartonella, Haemobartonella, Eperythrozoon, and Grahamella).

Discovery Discovered form of tick-borne typhus first described in the Rocky Mountain section of the United States, caused by a specific microorganism (Rickettsia rickettsii). Discovery of the microbe of Rocky Mountain spotted fever in 1906 by Howard Taylor Ricketts led to the understanding of other rickettsial diseases.

General characteristics • Highly pleomorphic bacreria that can present as cocci (0.1 μm in diameter), rods (1–4 μm long) or thread-like (10 μm long). • Rickettsiaceae are Gram-negative, obligate intracellular bacteria (except Rochlimaea) that infect mammals and arthropods. • Gram stain poorly, but appear to be G• Stain readily with Giemsa . • Traditional biochemical tests are useless because it can’t cultivated in ordinary medias.

Classification • Usually rickettsia classified by the disease it cause to two groups : 1. Spott fever group (SFG)

Rickettsia prowazekii , R. mooseri , R. felis 2.typhus group (TG)

R. rickettsii , R. conorii , R. sibirica , R. japonica , R. australis , R. akari

Natural cycle

Rickettsia species

Disease

Vectors

Hosts

Geographic distribution

Typhus group:

Rickettsia prowazekii R. mooseri R. felis

Epidemic typhus

Human Humans body lice

Worldwide

Recrudescent typhus

None

Humans

Worldwide

Murine typhus

Fleas

Rodents

Worldwide

(Endemic typhus)

Fleas

Opossums

USA

Murine typhus like

Fleas

Opossums

USA

Spotted Fever group:

R. rickettsii

Rocky Mountain spotted fever

Ticks

Small mammals, North & South dogs, rabbits, birds America

R. conorii

Boutonneuse fever

Ticks

Rodents, dogs

Africa, Southern Europe, India

R. sibirica

North Asia tick typhus

Ticks

Rodents

Eurasia, Asia

R. japonica

Japanese spotted fever

Ticks

Rodents, dogs

Japan

R. australis

Queensland tick typhus

Ticks

Rodents

Australia

R. akari

Rickettsialpox

Mites

House mice, rats

Worldwide

Virulence factors 1. Group specific soluble antigens compose from lipopolysaccharide and consider from the major cell wall component, used in vaccine production. 2. Species specific antigen Used to differentiate between rickettsia species, heat labile antigen. 3. Alkali stable polysaccharide antigen Found in many rickettsiae and is shared by certain strains of Proteus vulgaris.

4. Endotoxin and the production of immune complexes and hypersensitivity reactions.

5. The enzyme phospholipase A may help penetration. 6. Induced phagocytosis and recruitment of actin for intracellular spread. 7. R. Canadensis haemolyses red blood cells, is susceptible to erythromycin.

Pathogenicity On entry to human body Organism multiplies locally & enters the blood stream

Invades the vascular endothelial cells. Leading to proliferation of cells, and perivascular infiltration

Resulting in thrombosis of vessels Rupture and necrosis

Diseases and transmission routes • Typhus fever Group: 1. Epidemic typhus (Classical typhus) R.prowazekii.

2. Recrudescent infection (Brill–Zinsser). R.prowazekii 3. Endemic typhus (murine typhus) R. mooseri (R.typhi).

• Spotted fever group: 1. Rocky mountain spotted fever (RMSF) R. rickettsii.

2. Other tick borne diseases R. siberica, R. conori, R. australis . 3. Rickettsial pox R. akari .

Epidemic typhus •Causative organism: R.prowazekii . Vector: Pediculus humanus corporis (human body louse). Transmission: Autoinoculation by the person while scratching the bite of infected body louse –produce abrasion- which is portal of entry for the organisms. Incubation Period: 6-15 days. It is associated with wars & poverty. It is found in Africa & South America but not in United States. Symptoms: Chills, fever, headache, pain, stupor and delerium. Signs of severe meningoencephalitis, begin with rash. If untreated - death occurs due to peripheral vascular collapse or due to bacterial pneumonia. R. prowazekii is the agent of epidemic typhus. During World War I, approximately 3 million deaths resulted from infection by this bacterium. In World War II, the numbers were similar. This agent is carried by the human louse; therefore, disease is a consequence of overcrowding and poor hygiene.

Rocky mountain spotted fever (RMSF) • • • • • • • • •  

Causative organism: R. rickettsii . Vectors: Dermacentor variabilis (dog tick). Reservoirs: Dogs & rodents . Transmission: is via tick bite . The organism is passed by the transovarian route from tick to tick. Humans are accidental hosts. Incubation Period: 3-14 days. Mainly seen in children during spring & early summer – ticks are active. Symptoms: Sudden onset of fever, severe headache, mayalgia. In 2-6 days, a typical rash is seen. It begins with macules and progress to petechiae.  The rash appears on the hand and feet & spreads inwards to the trunk.  It can be fatal if untreated

Cultural characters • Do not grow on cell-free media. • They can be cultivated in the yolk sacs of embryonated eggs. • Can be cultivated on cell cultures –HeLa, HEp2, Detroit 6 etc. • Laboratory animal like mice is used for primary isolation . • The following nutrients are added to cell media : serine , glycine , Other nonessential amino acids, additional glucose, and potential products.

Weil-Felix test • Weil-Felix test is based on cross reaction of the rickettsial antigen with the O antigen polysaccharide found in Proteus vulgaris OX-19, OX-2 and OX-K. • The test measures the antiricketssial Ab in patient’s serum.

Sample collection • Coetaneous lesions are the symptoms which is in common between all rickettsial diseases, so, sample obtain mainly from skin lesions.

Identification • If you do a skin biopsy, you can make a diagnosis in a day or so. Some people don’t bother to do a biopsy. Although the biopsy is 100% specific, it sometimes gives dangerous false negative reports. • Later, you can confirm your diagnosis by doing tests for antibodies, or serology. • The old tests, the Weil-Felix tests, are now archaic. • Laboratories now have immunofluorescent antibody (IFA), or ELIZA assays. • The problem is that you have to wait a couple weeks before you can expect the antibodies to develop and draw the blood for the convaslescent titers.

world distribution R. mongolotimonae

R. conorii Astrakhan R. sibirica

R. helvetica

« R. heilongjiangii »

R. mongolotimonae R. conorii Israël

R. helvetica

R. slovaca R. conorii

R. conorii Israël

R. japonica

R. conorii R. rickettsii

Indian tick typhus Rickettsia R. conorii R. australis R. africae R. honei

Treatment & VACCINES • Treatment Tetracycline and chloramphinicol is the antibiotic of choice (because of the small molecule size and the ability to penetrate infected cells). • VACCINES Killed or attenuated live vaccines for epidemic and endemic typhus, Rocky Mountain spotted fever and scrub typhus have been available for many years. Recombinant DNA methods are now being investigated.

References • • • • • • •

MIMS: chapter 21. Levinson: chapter 26. Bairley: chapter 39. Emanuel: chapter 28. Jawetz: chapter 27. Kayser: unit 4. http://www.textbookofbacteriology.net/Rick ettsia_2.html. • http://en.wikipedia.org/wiki. • http://www.cehs.siu.edu/fix/medmicro/ricke. htm. • others.