2. Synopsis
• Genus Rickettsia
• Genus Orientia
• Genus Ehrlichia
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• Genus Coxiella
• Genus Bartonella
3. Introduction
• Intracellular growth
• Transmitted by blood sucking arthropod
vectors
• Howard Taylor ricketts (1906) – Discovered
spotted fever rickettsia – died of typhus fever
contracted during his studies
4.
5. Characteristics
• Small GNB
• Virus like , cannot be seen under ordinary light
microscope
• Obligate intracellular parasite
10. • Pathogenesis:
Lice become infected by feeding on
ricketssiaemic patients multiply in the gut
of lice appear in feces in 3 to 5 days
infection transmitted from person to person
• When the contaminated louse feces is rubbed
through the minute abrasions caused by
scratching
• Occasionally by aersols of dried louse feces
through inhalation or through the conjuctiva
11. • Incubation period is 5 to 15 days
• Fever with chills
• Characteristic rash – 4th or 5th day
• Stuporous and delirious
• Case fatality – 40%
13. Recrudescent typhus
• Latent infection in whom recovered from
epidemic typhus
• Reactivation
• Hence no extrahuman reservoir
14. Endemic typhus
• Causative agent: R. typhi
• Host: Rats, Humans
• Vector: Flea – Xenopsylla cheopsis
• Pathogenesis:
Rickettsia multiplies in the gut of the flea shed in
faeces humans
16. • Humans acquire the disease:
1. The bite of infected fleas, when their saliva or
feces is rubbed in
2. Through aerosols of dried feces
3. By ingesting food recently contaminated with
infected rat urine or flea feces
Human infection is a dead end
PERSON TO PERSON TRANSMISSION DOES NOT
OCCUR
17. SPOTTED FEVER GROUP
• Common soluble antigen
• Multiply in the nucleus as well as in the
cytoplasm of host cells
• All transmitted by ticks except R.akari (Mite
borne)
• Tick typhus
• Rickettsial pox
18. Tick typhus
• Transovarian transmission – in ticks – both
vector and reservoir
• Larval stage or adult ticks – infective form to
vertebrate hosts
• Transmitted to human by tick bite
20. • Rocky mountain spotted fever – most serious
type
• Causative agent : R.rickettsii
• Indian tick typhus – R.conori
• Tick: Rhipicephalus sanguineus
21. Rickettsial pox
• Self limited, non fatal, vesicular exanthem
• Similar to chicken pox
• Vesicular or varicelliform rickettsiosis
• Causative agent: R.akari
• Reservoir : Domestic mouse
• Vector : mite (Transovarial transmission)
22. Pathogenesis in humans
• Transmitted to humans by arthropod vectors
through bite or feces
• Ricketssaie multiply locally and enter the
blood
• Localised chiefly in the vascular endothelial
cells thrombus formation occlusion of
vascular lumen
23. • Clinical features : acute febrile illness,
septicemia with maculopapular rash and fever
• The long survival of rickettsiae in various
organs and lymphatic tissues in infected
humans and animals is a distinctive feature in
its pathogenesis.
26. Morphology
• Pleomorphic coccobacilli
• Non motile , non capsulated
• 0.3 – 0.6 * 0.8 – 2 um
• Gram negative, but do not stain well
• Under electron microscope three layered
cell wall
27. cultivation
• Unable to grow in cell free media
• Growth occurs in the cytoplasm of infected
cells
• Optimum temperature – 32 to 35deg C
• Cultivated in yolk sac of developing chick
embryos, also grow on HeLa, Hep-2, Detroit 6
continuous cell lines
28. Resistance
• Rapidly destroyed at 56degC
• Destroyed at room temp also
• Hence when seperated from host preserve
in skimmed milk or a suspending medium
containing sucrose, potassium phosphate and
glutamate (SPG medium)
29. Antigenic structure
• Spotted fever rickettsiae A, B proteins
• Third surface antigen alkali stable
polysaccharide found in some rickettsiae
and in some strains of the Proteus bacilli
31. Neil Mooser Reaction
• R.typhi and R.prowazekii – similar
• When male guinea pigs are inoculated
intraperitoneally with blood from a case of
endemic typhus or with a culture of R.typhi
develop fever and characteristic scrotal
inflammation.
• Scrotum enlarged and testes cannot be pushed
back into the abdomen because of inflammatory
adhesions between the layers of the tunica
vaginalis
• Neil – Mooser or tunica reaction
32.
33. GENUS ORIENTIA
SCRUB TYPHUS (CHIGGER BORNE TYPHUS):
• Causative agent: Orientia tsutsugamushi
• First observed in Japan
• Vector: trombiculid mites
• Mite islands
• Humans bitten by mite larvae (Chiggers)
• Transovarian transmission in mites
35. • Zoonotic tetrad O.tsutsugamushi, chiggers,
rats and secondary and transitional forms of
vegetation
• Incubation period – 1 to 3 weeks
• Characteristic Eschar, regional
lymphadenopathy and maculopapular rash
• Three antigenic types : Karp, Gilliam and Kato
36.
37. GENUS EHRLICHIA
• Small, Gram negative, obligate intracellular
bacteria
• Tick borne
• Cytoplasm of infected phagocytic cells
grow within phagosomes as mulberry like
clusters Morula
38. • Pathogenicity: Three infections
1. Resembles glandular fever. Causative agent is
Ehrlichia sennetsu. Endemic in Japan. Causes
lymphoid hyperplasia and atypical
lymphocytosis. No arthropod vector. Human
infection is suspected to be caused by
ingestion of fish with flukes
39. • 2. Human monocytic ehrlichiosis – caused by
Ehrlichia chaffeensis. Transmitted by
Amblyomma ticks. Deer and rodents are
reservoir hosts. Human disease with
leukopenia, thrombocytopenia and elevated
liver enzymes
40. • 3. Human granulocytic ehrlichiosis – either
identical with or closely related to equine
pathogen Ehrlichia equi. Transmitted by ticks.
Deer, cattle and sheep are the suspected
reservoir. Leucopenia and thrombocytopenia
are seen in patients
• Treatment: Doxycline for ehrlichiosis
43. Direct Microscopy
• Light microscope cant see individual
organism, only aggregations of rickettsial
particles
• Giemsa stain purple coloured basophilic
inclusions
• Machiavello stain red coloured inclusions
• Immunofluorescence microscope skin
biopsies from the centre of the petechial
lesions
44.
45. Culture
• Yolk sac of embryonated hen`s eggs
• Male guinea pigs or mice
• Tissue culture
46. Serological test
Weil felix reaction:
• Agglutination test in which sera are tested for
agglutinins to the O antigens of certain non
motile Proteus strains OX 19, OX2, OX K
• Due to sharing of antigen by ricketssiae and
certain strain of proteus
• Tube agglutination test
52. GENUS COXIELLA
• Coxiella burnetii
• Causative agent of Q fever ( Query)
• Pleomorphic bacilli
• Obligate intracellular pathogen
• Differs from rickettsia by being
1. More resistant to heat
2. No vector
54. • Weil felix test cannot be used to diagnose
• Infection is from cattle , sheep and goats
• Zoonotic disease
• Bandicoot are the reservoir
• Transmitted to cattle by ixodid ticks
• Shed in milk of infected animals and
transmitted to humans
55. Pathogenicity
• Human disease characterised by interstitial
pneumonia
• Coxiella may remain latent in the tissues of
patients of 2 to 3 years
59. GENUS BARTONELLA
• Tiny GNB
• Transmitted by arthropods
• Pathogenic strains
1. B.bacilliformis
2. B.quintana
3. B.henselae
60. Bartonella bacilliformis
• Oroya fever
• High mortality
• Late sequel verruga peruana
• 1885 – Medical student Daniel Carrion
inoculated himself with material from verruga
and developed oroya fever and died
• Carrion`s disease
61. Bartonella quintana
• First world war trench fever or five day
fever (Million of cases)
• No animal reservoir
• Transmitted by body louse
• Ability to grow in blood agar
62. Bartonella henselae
• Febrile illness with lymphadenopathy
following a cat scratch Cat scratch disease
• Isolated from the blood of patients in blood
media after prolonged incubation
• Demonstrated in lymph node biospy smears
and sections by Warthin-Starry staining
63. • Associated with HIV infected and
immunodeficient personns
• Bacillary angiomatosis