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Veterinary Bacteriology & Mycology > Rickettsiales > Flashcards

Rickettsiales Flashcards

1
Q

How does the presence of LPS and peptidoglycan differ in Anaplasma, Rickettsia, and Ehrlichia?

A
  • Anaplasma and Ehrlichia lack LPS
  • Rickettsia has LPS

~ Anaplasma and Ehrlichia have minimal peptidoglycan
~ Rickettsia has the classical peptidoglycan (very similar to other Gram-negative bacteria)

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2
Q

Since Anaplasma and Ehrlichia lack LPS, what maintains cell wall stability?

A

acquire cholesterol from their host

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3
Q

What are the 2 morphotypes of Anaplasma and Ehrlichia?

A
  1. EXTRACELLULAR: dense-cored cell (DC)
  2. INTRACELLULAR: reticulate cell (RC- morula)
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4
Q

How do the intracellular morula of Anaplasma and Ehrlichia behave? How does Rickettsia compare?

A

replicate in vacuoles (like Chlamydia and Salmonella)

lacks 2 different life forms and does not hide in vacuoles (like Listeria and Yersinia)

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5
Q

Why are Rickettsiales members obligate intracellular pathogens?

A
  • cytoplasmic membranes of Anaplasma, Ehrlichia, and Rickettsia are highly permeable
  • Anaplasma, Ehrlichia, and Rickettsia cannot produce enough of their own ATP
  • Anaplasma and Ehrlichia are dependent on cholesterol from their host cell to stabilize their cell envelop
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6
Q

How are Anaplasma and Ehrlichia transmitted?

A

arthropod-borne —> ticks

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7
Q

What are the 4 groups of Rickettsia? How is each transmitted? What 3 characteristics are used for this differentiation?

A
  1. spotted fever group - Dermacentor ticks
  2. ancestral group - ticks
  3. typhus group - fleas, lice
  4. transitional group - ticks, mites, fleas
  • LPS serogrouping
  • arthropod vectors
  • clinical manifestations
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8
Q

What is required for Anaplasma, Ehrlichia, and Rickettsia transmission? Why?

A

arthropods

  • cannot stay outside of a cell for a long time
  • arthropods are able to directly deposit them into or near blood vessels so they can immediately infect blood cells or endothelium
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9
Q

How do the arthropod vectors of each Rickettsiales member transmit them?

A

RICKETTSIA - various arthropod larvae, nymph, and adults exhibit transstadial and transovarian transmission

ANAPLASMA, EHRLICHIA = only nymph and adult ticks undergo transstadial transmission

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10
Q

Why does there seem to be a predilection for ticks for Rickettsiales transmission?

A

ticks hunt animals for blood meal and there are at least 3 stages in their life where they have a high chance of transovarian and transstadial transmission

  • TO = larvae climb onto host, get a blood meal, and engorged larvae drop in vegetation
  • TS = nymph climbs onto host, gets a blood meal, and engorged nymph drops in vegetation
  • TS = adult ticks climb on host, get a blood meal, and engorged females drop in vegetation where they lay eggs
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11
Q

What are the 4 most medically important ticks in the US?

A
  1. Rhipicephalus sanguineus - brown dog tick
  2. Amblyomma americanum - lone star tick
  3. Dermacentor variabilis - dog tick
  4. Ixodes scapularis - eastern black-legged tick
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12
Q

What are the general predilection sites for Rickettsiales in vertebrates? Specific genera?

A

blood cells and endothelial cells

  • Anaplasma = RBC, WBC, platelets
  • Ehrlichia = WBC, endothelium
  • Rickettsia = endothelium
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13
Q

What are the 2 predilection sites of Rickettsiales in arthropods?

A
  1. midgut cells
  2. salivary glands
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14
Q

Which 3 species of Anaplasma target red blood cells? What does this cause?

A
  1. A. marginale - Rhipicephalus, Dermacentor, Hyalomma, Boophilus, Ixodes
  2. A. centrale - Rhipicephalus, Dermacentor
  3. A. ovis - Rhipicephalus, Dermacentor

ANEMIA

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15
Q

What species of Anaplasma targets red blood cells, monocytes, and macrophages? What does this cause?

A

A. bovis - Rhipicephalus, Hyalomma, Ambylomma, Haemaphysalis

anemia and leukopenia (lowers immunity —> higher chance of secondary infection)

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16
Q

What species does Anaplasma particularly target? What are 2 exceptions and what do they cause?

A

ruminants

  1. A. phagocytophilum - all mammals, dogs + humans (Ixodes scapularis) —> neutrophils —> leukopenia
  2. A. platys - dogs (Rhipicephalus, Dermacentor) —> platelets —> thrombocytopenia (bleeding)
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17
Q

What are the 3 species of Ehrlichia affecting dogs? What do they target?

A
  1. E. chaffeensis - Amblyomma, Dermacentor; monocytes, macrophages (ZOONOTIC)
  2. E. ewingii - Amblyomma, Dermacentor; neutrophils (ZOONOTIC)
  3. E. canis - Rhipicephalus; monocytes, macrophages

LEUKOPENIA

18
Q

What 2 species of Ehrlichia affect ruminants? What do they target?

A
  1. E. chaffeensis - Amblyomma, Dermacentor; monocytes, macrophages (ZOONOTIC)
  2. E. ruminantum - Amblyomma; endothelium

LEUKOPENIA + VASCULITIS + THROMBOCYTOPENIA = heartwater disease

19
Q

What is the major predilection site of Rickettsia? What are the 4 major species affecting humans and rodents? What disease do they cause and how are they transmitted?

A

blood vessels —> bleeding

  1. R. prowazekii - epidemic (sylvantic) typhus - lice transmit to humans and flying squirrels
  2. R. typhi - murine typhus - fleas transmit to humans and wild rodents
  3. R. akari - Rickettsial pox - mites transmit to humans and wild rodents
  4. Orentia tsutsugamushi - scrub typhus - mites transmit to humans and wild rodents
20
Q

What 2 species of Rickettsia affect dogs and cats? Why do they cause and how are they transmitted?

A
  1. R. rickettsii - Rocky Mountain spotted fever - Dermacentor and Amblyomma ticks transmit to humans, dogs, wild rodents, voles, and small mammals
  2. R. felis - cat flea rickettsiosis - fleas transmit to humans, cats, rodents, and opossums
21
Q

What are the 5 major uses of the proteins produced by Anaplasma, Ehrlichia, and Rickettsia?

A
  1. adhesion
  2. internalization
  3. survival
  4. replication
  5. lysis of RBC or endothelial cells
22
Q

What 3 proteins are used by Anaplasma, Ehrlichia, and Rickettsia for adhesion/attachment?

A
  1. outer membrane protein A - Anaplasma, Ehrlichia, Rickettsia
  2. outer membrane protein B - Ricketssia
  3. entry-triggering protein E - Anaplasma, Ehrlichia, Rickettsia
23
Q

What 2 groups of proteins produced by Anaplasma, Ehrlichia, and Rickettsia are responsible for producing lipid rafts (vesicles) for engulfing red blood cells and endothelial cells membranes?

A
  1. EtpE, clathrin, caveolin-2 - Anaplasma, Ehrlichia
  2. clathrin, caveolin-2 - Rickettsia
24
Q

What 4 proteins are produced by Anaplasma and Ehrlichia to survive in the vacuoles in the cytoplasm of host cells? Why doesn’t Rickettsia produce them?

A
  1. early endosome antigen 1
  2. Rab5A
  3. Rab7
  4. vacuolar-type H+ ATPase

Rickettsia survives freely in the host cytoplasm

25
Q

What 3 proteins are responsible for Anaplasma and Ehrlichia survival in the cytoplasm and morula formation?

A
  1. Rab7
  2. transient receptor potential channels (TRP)
  3. ECH0825
26
Q

What 2 enzymes are used by Rickettsia to destroy the vacuoles in the cytoplasm of host cells?

A
  1. hemolysin C
  2. phospholipase D

able to freely move and replicate in the cytoplasm of host cells

27
Q

In what 4 ways can Anaplasma, Ehrlichia, and Rickettsia spread to adjacent cells from infected RBCs and endothelial cells?

A
  1. protrusion of infected cell membranes (filopodia) to enter adjacent cells without bacteria entering the extracellular space - A, E
  2. packed blood cells burst to spread to the adjacent cells - A, E
  3. phospholipase A2 lyses infected cells - R
  4. budding from host cell membrane - R
28
Q

What are morula?

A

micro-colonies produced by Anaplasma and Ehrlichia when they multiply within the vacuoles in the cytoplasm of midgut or salivary gland cells of arthropods or vertebrate blood cells

29
Q

Anaplasma and Ehrlichia life cycle:

A
30
Q

Rickettsia lifecycle:

A
31
Q

What are the 10 most common clinical symptoms of Anaplasma, Ehrlichia, and Rickettsia infection?

A
  1. fever
  2. malaise
  3. muscle aches
  4. headaches
  5. nausea
  6. vomiting
  7. fatigue
  8. chills
  9. rash
  10. joint pain
  • very non-specific
32
Q

What are 3 unique symptoms of Anaplasma and Rickettsia infection?

A
  1. jaundice - Anaplasma
  2. bleeding (thrombocytopenia) - Anaplasma
  3. blood vessel thrombosis, occlusion, and necrosis - Rickettsia
33
Q

What is the cause of Rickettsia infection symptoms? What are the 6 most common symptoms?

A

disseminated endothelial infection due to lysis of capillaries in all organs

  1. vasculitis
  2. bleeding from skin (rash)
  3. bleeding from nose (epistaxis)**
  4. hemorrhage
  5. thrombosis
  6. blood vessel occlusion/necrosis
34
Q

What are the 9 most common organ failures caused by Rickettsia that can lead to death?

A
  1. encephalitis
  2. myocarditis —> CHF
  3. pneumonia
  4. nephritis
  5. hepatitis
  6. rash
  7. edema
  8. hypovolemia —> shock
  9. thrombocytopenia from hemorrhage
35
Q

What samples can be taken from humans/animals for Ricketssiales isolation?

A
  • blood spot smear
  • whole blood or serum
  • skin biopsy of eschar or rash
36
Q

What is the gold standard serological test for Ricketssiales identification? What else can be done?

A

indirect immunofluorescent IgG assay

  • species-specific ELISA
  • Weil Felix test
  • direct visualization in tissue samples with labeled antibodies
37
Q

What genes can be used on PCR to identify Rickettsiales? What 3 media can be used to culture them?

A

gItA, ompA, ompB, 16S genes —> quick, convenient

cell lines
1. tick cell lines - midgut cells, salivary gland cells, tick embryonic cells
2. mammalian endothelial cell lines
3. human leukemia cell lines

38
Q

What is the Weil-Felix test? What is a major disadvantage to this test?

A

serological test using Proteus species’ LPS antigens to cause a cross-reaction with Rickettsia antigens —> coagulation = positive

low sensitivity and specificity —> will cause agglutination in the presence of Proteus and Rickettsia

39
Q

What 3 species of Proteus are used in the Weil-Felix test?

A
  1. P. vulgaris OX19 - typhus group Rickettsia
  2. P. vulgaris OX2 - spotted fever group Rickettsia
  3. P. mirabilis OXK - scrub typhus group Rickettsia
40
Q

What are the 3 major aspects of the iceberg concept with Anaplasma, Ehrlichia, and Rickettsia infection?

A
  1. subclinical infections are common
  2. reservoir vertebrate hosts are widely distributed as a source of infection
  3. several genera and species of arthropods may get an infection and remain infected for life in the cases of Rickettsia or pass onto offspring
41
Q

What are 3 possible treatments for Rickettsiales cases?

A
  1. Doxycycline**
  2. Chloramphenicol
  3. Tetracycline
42
Q

What are the best 3 ways to control and prevent Rickettsiales cases?

A
  1. kill Anaplasma, Ehrlichia, and Rickettsia by prophylactic use of Doxycycline, Chloramphenicol, or tetracycline
  2. kill arthropods each season using spot-on, sprays, dust, or dipping of ascaricides (pyrethroids)
  3. boost resistance of animals with vaccines, feeding, indoor rearing, and stress avoidance

Veterinary Bacteriology & Mycology (47 decks)

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