II-A. Systemic Bacteriology | 25. Rickettsia

Question 1

I. Rickettsia genus
1. What are the main features of Rickettsia genus?

Answer 1

1. Intracellular, Gram-negative coccobacilli
2. Could be categorised based on clinical diseases
   - typhus group
   - spotted fever group

Question 2

I. Rickettsia genus
2. Give the classification based on clinical diseases?

Answer 2

Question 3

I. Rickettsia genus
3. What are the species of typhus group?

Answer 3

• R. prowazekii ➡ (epidemic) typhus
• R. typhi ➡ endemic typhus

Question 4

I. Rickettsia genus
4. What are the species of spotted fever group?

Answer 4

• R. rickettsii
• R. conorii

Question 5

II. Rickettsia prowazekii
1. What is the source of infection of Rickettsia prowazekii?

Answer 5

infected person

Question 6

II. Rickettsia prowazekii
2. What is route of transmission of Rickettsia prowazekii?

Answer 6

by the bite of body louse (Pediculus humanus)

Question 7

II. Rickettsia prowazekii
3. What are the 2 diseases caused by Rickettsia prowazekii?

Answer 7

• epidemic (exanthematic) typhus
• Brill-Zinsser disease: reactivation

Question 8

II. Rickettsia prowazekii
4. What are the features of epidemic (exanthematic) typhus?

Answer 8

• high fever, headache
• rash (present on palms, soles, and face as well!)
• confusion
• mortality is high (c.a. 40%) in untreated cases!

Question 9

II. Rickettsia prowazekii
5. What are the features of Brill-Zinsser disease?

Answer 9

Brill-Zinsser disease: reactivation
* usually milder than the primary disease
* infectious!

Question 10

II. Rickettsia prowazekii
5. What are the features of Brill-Zinsser disease?

Answer 10

Brill-Zinsser disease: reactivation
* usually milder than the primary disease
* infectious!

Question 11

III. Rickettsia typhi
1. What is the source of infection of Rickettsia typhi?

Answer 11

Rodents (rats – zoonotic!)

Question 12

III. Rickettsia typhi
2. What is the route of transmission of Rickettsia typhi?

Answer 12

through the bite of rat flee (vector- borne!)

Question 13

III. Rickettsia typhi
3. What is the disease caused by Rickettsia typhi?

Answer 13

• high fever, headache
• rashes (palms - soles - face are usually spared!)
• disturbed state of consciousness

Question 14

IV. Rickettsia rickettsii
1. Wha is the source of infection of Rickettsia rickettsii?

Answer 14

wild animals (zoonotic)

Question 15

IV. Rickettsia rickettsii
2. What is the route of transmission of Rickettsia rickettsii?

Answer 15

by the bite of ticks (Dermacentor species)

Question 16

IV. Rickettsia rickettsii
3. What is the pathomechanism of Rickettsia rickettsii?

Answer 16

• infects capillary endothelial cells, spread from cell to cell
• causes vasculitis (inflammation of vessels) in different organs

Question 17

IV. Rickettsia rickettsii
4. What is the disease caused by Rickettsia rickettsii?

Answer 17

Rocky-mountain spotted fever (RMSF)
- flu-like symptoms after a week of incubation
- rash usually starts on the wrists, ankles then spread to other parts of
the body (face is usually spared!)
- mortality is high (20%) if left untreated!

Question 18

V. Rickettsia conorii
1. What is the source of infection of Rickettsia conorii?

Answer 18

wild animals (zoonotic)

Question 19

V. Rickettsia conorii
2. What is the route of transmission of Rickettsia conorii?

Answer 19

by the bite of ticks

Question 20

V. Rickettsia conorii
3. What is the pathomechanism of Rickettsia conorii?

Answer 20

• infects capillary endothelial cells, spread from cell to cell
• causes vasculitis (inflammation of vessels) in different organs

(similar to RMSF)

Question 20

V. Rickettsia conorii
3. What is the pathomechanism of Rickettsia conorii?

Question 21

V. Rickettsia conorii
4. What is the disease caused by Rickettsia conorii?

Answer 21

mediterranean spotted ever
* similary to RMSF
* rash is usually present on the face as well

Question 22

VI. Diagnosis of Rickettsia and Orientia infections
1. What is the diagnosis of Rickettsia and Orientia infections?

Answer 22

Question 23

VI. Diagnosis of Rickettsia and Orientia infections
2. How do we do laboratory for Diagnosis of Rickettsia and Orientia infections

Answer 23

serology (it takes time for antibodies to be produced!)
1. immunofluorescence (IF): detection of anti-Rickettsia (anti-Orientia) antibodies from patient’s serum
2. Weil-Felix tube agglutination: etection of anti-Rickettsia antibodies from patient’s serum

Question 24

VI. Diagnosis of Rickettsia and Orientia infections 3. How do we perform immunofluorescence (IF) for Diagnosis of Rickettsia and Orientia infections?

Answer 24

Detection of anti-Rickettsia (anti-Orientia) antibodies from patient’s serum - pre-made slides (containing Rickettsia / Orientia) antigens are incubated with patien’s serum, then secondary, fluorophore labeled antibodies are added, and the slide is examined under a fluorescent microscope

Question 25

VI. Diagnosis of Rickettsia and Orientia infections 4. How do we perform Weil-Felix tube agglutination for Diagnosis of Rickettsia and Orientia infections?

Answer 25

Detection of anti-Rickettsia antibodies from patient’s serum - certain proteins of Rickettsia are quite similar to the proteins of Proteus vulgaris OX19 - we mix the patients serum with proteins of Proteus vulgaris OX19 - if agglutination is present, we could say that the patient MIGHT HAS antibodies against Rickettsia

Question 26

VII. What is the empirical therapy for Rickettsia and Orientia infections?

Answer 26

tetracyclins (doxycyclin)