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Rickettsia

Rickettsia are obligate intracellular bacteria resembling viruses, characterized by poor Gram staining and a cell wall similar to Gram-negative bacilli. They are divided into three antigenically distinct groups: Typhus, Scrub typhus, and Spotted fever, each associated with specific diseases, vectors, and clinical features. Laboratory diagnosis primarily involves serologic testing, with treatment options including tetracycline and chloramphenicol.

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7 views15 pages

Rickettsia

Rickettsia are obligate intracellular bacteria resembling viruses, characterized by poor Gram staining and a cell wall similar to Gram-negative bacilli. They are divided into three antigenically distinct groups: Typhus, Scrub typhus, and Spotted fever, each associated with specific diseases, vectors, and clinical features. Laboratory diagnosis primarily involves serologic testing, with treatment options including tetracycline and chloramphenicol.

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tashfia.haque11
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Rickettsia

DR. SHEIKH JOLY FERDOUS ARA


ASSISTANT PROFESSOR
DEPARTMENT OF MICROBIOLOGY
AHSANIA MISSION MEDICAL COLLEGE
Outlines
General characteristics of Rickettsia
Antigenic structures
Clinical features
Lab Diagnosis
Question /Answer session
Obligate Intracellular bacteria
Rickettsia
Chlamydia
What are the other obligate intracellular organism?
Virus
Rickettsia
Resemble virus
Short rods or cocci, single/ pair, chains or filaments
Stain poorly by Gram stain
Giemsa stain: It appears blue
Cell wall resemble Gram negative bacillus
Vector borne (except Q fever)
They exhibit fever, rash and vasculitis (except Q fever)
Contd…
Divided into 3 antigenically distinct groups:
1.Typhus
2.Spotted fever
3.Scrub typhus
Contd..
Organism Disease Geographic Vector Clinical
distribution features

A. Typhus Epidemic typhus Worldwide Louse fever,


group (S.am,Africa,Asia) headache, rash,
R.prowazekii chill (severe if
untreated)

R. typhi Murin typhus, Worldwide Flea Same but


Endemic typhus milder than
epidemic
typhus
Contd..
Organism Disease Geographic Vector Clinical features
distribution
B. Scrub Scrub Asia, Mite fever,headache,rash
typhus group typhus South pacific ,
lymphadenopathy,
R.tsutsugamusi atypical
lymhocyte
Contd..
Organism Disease Geographic Vector Clinical
distribution features
C. Spotted Rocky USA, S A Tick fever,
fever group Mountain headache, rash
R. rickettsii spotted fever systemic
manifestation

R. akari Rickettsial USA, Russia Mite fever,


pox headache,
rash,
(mild)
Contd..
Organism Disease Geographic Vector Clinical
distribution features
Others Q fever Worldwide None Headache,
Coxiella fever,
burnetii fatigue,pneum
onia, no rash.
Typical lesion is
Rash
Oedema
Haemorrhage
Clinical features
Vasculitis
Fever
Headache
Rash
Lymphadenopathy
Laboratory Diagnosis
A. Culture is difficult, not done routinely
B. Serologic diagnosis is done
1. Weil-Felix Reaction
Agglutination test
Antibody titer of patient is observed
A rising titer (4 fold rise)
Contd. OR
1/80 is diagnostic.
Nonspecific test
Reagent used: O-antigen of Proteus
(Proteus ag. has antigenic similarity with Rickettsial ag.)
Proteus: OX-2, OX-19, OX- K strains are used
Treatment
Tetracycline
Chloramphenicol.
Question /Answer session
Q. A 40-year-old woman gets high fever, headache, and rash
on her body and palms. She dies despite treatment. Tests
show Rickettsia rickettsii. What is most accurate?
(A) She lived in Colorado and was bitten by a tick.
(B) She lived in Colorado and was bitten by a mosquito.
(C) She lived in Virginia and was bitten by a tick.
(D) She lived in Virginia and was bitten by a flea.
(E) She lived in Connecticut and was bitten by a mosquito
THE END

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