Rickettsiaceae

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Rickettsiaceae

  1. 1. Rickettsiaceae Gram –ve bacilli
  2. 2. <ul><li>Obligate intracellular parasites of flee-GIT of arthropod </li></ul><ul><li>In humans –infect vascular endothelial and reticuloendothelial cells </li></ul><ul><li>Spotted fever -fever with rashes </li></ul><ul><li>Howard Taylor ricketts- 1906 </li></ul>
  3. 3. <ul><li>Genus Rickettsia </li></ul><ul><li>Genus Orienta </li></ul><ul><li>Genus Ehrlichia </li></ul><ul><li>Genus Coxiella </li></ul><ul><li>Bartonella </li></ul>
  4. 4. Genus Rickettsia <ul><li>Typhus fevers and spotted fevers </li></ul><ul><li>Morphology </li></ul><ul><li>Coccobacillary-nonmotile,noncapsulated,cannot be stained with gram stain,geimsa stain used </li></ul><ul><li>Electron microscop-structure similar to gram –ve bacilli </li></ul><ul><li>3 layerd cell call </li></ul>
  5. 5. Cultivation <ul><li>Unable to grow in cell free media </li></ul><ul><li>In cytoplasm of infected cells </li></ul><ul><li>But in spotted fever-growth may take place in nucleus as well </li></ul><ul><li>Rickettsiae grows better in cells that are not metabolising </li></ul><ul><li>Yolksac of chick embryos,hela,hep2,detroit6 </li></ul><ul><li>Tissue cultures not satisfactory </li></ul><ul><li>Inoculation </li></ul><ul><li>Propagated in arthopods </li></ul>
  6. 6. Antigenic structure <ul><li>Group and Species specific antigens </li></ul><ul><li>Surface protein Antigens (SPA)-R.prowazekii &R.typhi-species specific+cross reactive epitopes </li></ul><ul><li>Outer Menmbrane Proteins(OMP)-A & B-in spotted fever R. </li></ul><ul><li>A-adhesion species specific </li></ul><ul><li>Alkali stable polysaccharide SAnitigen-found in R.and proteus bacilli </li></ul>
  7. 8. <ul><li>Weil-Felix reaction -D/g of rickettsial infections by the demonstration of agglutinins to proteus strains </li></ul><ul><li>P.vulgaris( OX 19,OX2,) </li></ul><ul><li>P.mrabilis (OX K) </li></ul><ul><li>Basis of the reaction is the sharing of antigens between Rickettsia and proteus </li></ul>
  8. 9. Pathogenesis <ul><li>Arthopod bites and feces,minute abberations by scratching----multiplies locally---blood----localised in vascular endothelial cells,which enlarges ,degenerates,---thrombus formation---partial/complete occlusion of lumen </li></ul><ul><li>It may survive in lymphoid tissues and other organs for years </li></ul>
  9. 10. vaccines <ul><li>Weigl’s vaccine-phenolised intestinal content of lice infected p.r. with R.prowazekki </li></ul><ul><li>Castaneda-formalinised mouse-lung vaccine </li></ul><ul><li>Cox-inactivated yolk sac vaccine </li></ul>
  10. 11. Typhus fever group <ul><li>Includes </li></ul><ul><li>Epidemic typhus-R.prowezekii </li></ul><ul><li>Recrudescent typhus/Brill Zinsser disease-latent form of above </li></ul><ul><li>Endemic typhus-R.typhi </li></ul>
  11. 12. Epidemic typhus <ul><li>Louse born typhus </li></ul><ul><li>Host –humans </li></ul><ul><li>Vector-body louse-Pediculus humanus corporis </li></ul><ul><li>Incubation period-5-15 days </li></ul><ul><li>Fever ,chills,rashes-starting on trunks-spreading to limbs-sparing face palms and soles.2 nd week-stuporous,delirious </li></ul>
  12. 13. Endemic typhus <ul><li>Flee born typhus </li></ul><ul><li>Maintained in nature as a mild infection of rats </li></ul><ul><li>Vector—Xenopsylla cheopis/rat flea </li></ul><ul><li>Bite+ingestion of food contaminated with infected rat urine </li></ul><ul><li>Human infection is the dead end </li></ul><ul><li>No man –man transfer </li></ul>
  13. 14. <ul><li>R.typhi & R,prowazekii are closely similar </li></ul><ul><li>To differentiate- Neill-Mooser/Tunica reaction </li></ul><ul><li>It is negative with prowazekii </li></ul><ul><li>Infected blood of typhi---intra peritoneally--male guinea pig--- fever and scrotal inflammation-testis cannot be pushed back to abdomen due to inflammatory adhesions between the layers of tunica vaginalis </li></ul>
  14. 15. Spotted fever group <ul><li>Common soluble antigen,multiplies in nucleus as well as cytoplasm </li></ul><ul><li>Transmitted by ticks ,except R.akari-by mites </li></ul><ul><li>Two types </li></ul><ul><li>Tick typhus </li></ul><ul><li>Rickettsial pox </li></ul>
  15. 16. Tick typhus <ul><li>R.rickettsii-Rocky moutain spotted fever-first insect transmitted bacterial pahogen to be recognised </li></ul><ul><li>R.siberica-Siberian tick typhus </li></ul><ul><li>R.conori-indian tick typhus </li></ul><ul><li>R.australis,japonica,africae </li></ul>
  16. 17. <ul><li>Transmitted transovarially in ticks-both vectors & reservoirs </li></ul><ul><li>Infection to any vertebrates hosts by any of the larval stages/by adult ticks </li></ul><ul><li>They invades the salivary glands—bite </li></ul><ul><li>Rocky moutain spotted fever-transmitted by tick Dermacentor andersoni </li></ul>
  17. 18. Rickettsial pox <ul><li>Mildest rickettsial d/s </li></ul><ul><li>Self limited,non fatal, </li></ul><ul><li>Vesicular exanthem </li></ul><ul><li>Also called vericelliform rickettsiosis- similar to chicken pox </li></ul><ul><li>Causitive agent is –R. akari </li></ul><ul><li>Resevoiur- domestic mouse-Mus musculus </li></ul><ul><li>Vector-mite-Liponyssoides sanguineus- in which transoverial transmission occurs </li></ul>
  18. 19. Genus orientia-Scrub typhus- OXK +ve <ul><li>Chigger borne typhus </li></ul><ul><li>Caused by orientia tsugutsugumushivector-mites-belonging to the genus-Leptotrombidium </li></ul><ul><li>L.Lakamushi (japan)—L.deliensis (india) </li></ul><ul><li>Mites inhibit sharply demarkated areas in the soil- mite islands </li></ul><ul><li>Mite larvae(chiggers) in island---bites human— </li></ul><ul><li>Mite feeds on warm blooded animals only in the larval stage and the adult form feeds only on plants </li></ul>
  19. 20. <ul><li>Four factorsfor infection-O.tsu.,chiggars,rats,vegitations </li></ul><ul><li>Inc.p.-1-3 weeks </li></ul><ul><li>Eschar at thje site of bite,regional lymphadenopathy,maculopapular rash. </li></ul><ul><li>d/s sets in with fever,head ache ,conjunctival congestion------encephalitis and pneumoia </li></ul><ul><li>Three major antigenic types of O.tsu.- </li></ul><ul><li>Karp </li></ul><ul><li>Gilliam </li></ul><ul><li>kato </li></ul>
  20. 21. Genus –Ehrlichia/anaplasma/cowdria/neorickettsia <ul><li>Seen in cytoplasm of the infected phagocytes-grows within phagososmes-mulberry like clusters called morula </li></ul>
  21. 22. <ul><li>Tick borne </li></ul><ul><li>Three human d/s </li></ul><ul><li>Glandular fever like-E.sennetsu-lymphoid hyperplasia & atypical lymphocytosis—by ingestion of fish carrying infected flukes </li></ul><ul><li>Human monocytic ehrlichiosis-E.chaffeenis—amblyomma ticks—lecopenia,thrombocytopenia,elevated liver enzymes </li></ul><ul><li>Human granulocytic Ehrlichiosis-E.equi—ixode ticks—leucopenia,thrombocytopenia </li></ul><ul><li>T/t-Doxycycline </li></ul>
  22. 23. Genus –Coxiella-Q fever <ul><li>Coxiella burnetti—in group protobacteria </li></ul><ul><li>Obligate intra-primarily affecting monocyte-macrophage cells </li></ul><ul><li>Bandicoot---ixodid ticks---domestic cattles----human-occupation,milk </li></ul><ul><li>Coxiela may enter thru abraded skin—mucosa,lungs,intestinal tract </li></ul><ul><li>Iterstitial pneumonia,hepatitis,endocarditis, </li></ul><ul><li>Spotaneous reovery is usual </li></ul>
  23. 24. <ul><li>Shows phase variation-1 and 2 </li></ul><ul><li>Fresh isolates-phase 1 </li></ul><ul><li>On repeated passage thru yolk sac –phase 2 </li></ul><ul><li>Reverts to phase 1 on passing thru guinea pigs </li></ul><ul><li>Phase 1-a carbohydrate-per iodate sensitive-trichloro acetic acid soluble </li></ul><ul><li>1 are auto agglutinmable—phagocytosed in the absence of antibodies </li></ul><ul><li>1 is more powerful immunogen </li></ul><ul><li>t/t Doxacycline </li></ul>
  24. 25. Bartonella <ul><li>Gram –ve-transmitted by arthropods-invade mammelian endothelial cells and blood cells </li></ul><ul><li>Human pathogenic forms </li></ul><ul><li>B.bacilliformis </li></ul><ul><li>B.quintana </li></ul><ul><li>B.henselae </li></ul>
  25. 26. B.bacilliformis <ul><li>Oroya fevre/Carion’s disease-fever,progressive anaemia,bacterial invasion of erythrocytes—mortality is high if untreated </li></ul><ul><li>Verruga peruana-nodular ulcerating skin lesion </li></ul><ul><li>Gram neg. rod—motile </li></ul><ul><li>B.quintana-trench fever/5 day fever-not fatal-by body louse </li></ul>
  26. 27. B.henselae <ul><li>Febrile illness following lymphadenopathy following a cat scratch </li></ul><ul><li>Cat scratch disease </li></ul><ul><li>Also linked with two other conditions-seen commonly in hiv infected and immuno defficient </li></ul><ul><li>Bacillary angiomatosis-vascular node /tumours in skin </li></ul><ul><li>Bacillary peliosis-involves liver and spleen </li></ul>

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