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MHD 1 > L31 Rickettsia, Ehrlichia, and Related Bacteria > Flashcards

L31 Rickettsia, Ehrlichia, and Related Bacteria Flashcards

1
Q

What are the two genera in the Rickettsiaceae family?

A
  1. Rickettsia

2. Orientia

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2
Q

What is the important species of Orientia?

A

O. tsutsugamushi

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3
Q

What are the two groups of Rickettsia species?

A
  1. Spotted fever group

2. Typhus group

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4
Q

What are the 2 species of Rickettsia in the spotted fever group?

A
  1. R. rickettsii

2. R. akari

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5
Q

What are the 2 species of Rickettsia in the typhus group?

A
  1. R. prowazekii

2. R. typhi

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6
Q

Describe the structure of Rickettsia species.

A
  1. Small Gram Negative rods that stain poorly; LPS and peptidoglycan (except Orientia)
  2. Giemsa stain
  3. No flagella
  4. Divide via binary fission
  5. Slow growth over 9-12 hours
  6. Obligate intracellular
  7. Use host ATP, coA, NAD, amino acids
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7
Q

Describe the general pathogenesis of Rickettsiaceae organisms.

A

Enter the cell via phagocytosis. Escape the vacuole with phospholipase A, replicate freely in the cytoplasm. Move using cytoskeletal components (EXCEPT typhus types x3).

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8
Q

Describe the pathogenesis of Rickettsia rickettsii

A

OmpA adheres to endothelial cells. Bacteria multiply in the cells lining small blood vessels. This leads to cell damage, cell rupture, vasculitis, and a rash. Hypovolemia and hypoproteinemia occur via loss of plasma into the tissues.

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9
Q

Discuss the epidemiology of R. rickettsii.

A
  1. ~2000 cases annually in the U.S.

2. Majority of cases occur in South/Central United States

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10
Q

How is R. rickettsii transmitted?

A

Hard tick vectors (primarily in the summer); transovarian tramission

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11
Q

What is the reservoir of R. rickettsii?

A

Small rodents and dogs

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12
Q

What is the clinical manifestation of R. rickettsii?

A

Rocky mountain spotted fever

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13
Q

Describe the symptoms of RMSF. What is the incubation period?

A
  1. High fever, malaise, myalgias, nausea, vomiting, abdominal pain, diarrhea, severe headache
  2. Macular rash (extremities to the trunk); can become petechial

2-7 days, up to 2 weeks

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14
Q

How is RMSF daignosed?

A
  1. Symptoms/epidemiology

2. MIF assay (detects OMP and LPS)

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15
Q

What is the treatment for RMSF?

A

Doxycycline

Alternative: chloramphenicol (associated with higher relapse)

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16
Q

Discuss the epidemiology of R. akari.

A

Found in the US, Ukraine, Croatia, Korea

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17
Q

What is the vector of R. akari?

A

Bloodsucking mites (transovarian transmission)

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18
Q

What is the reservoir of R. akari?

A

Mice

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19
Q

Describe the clinical manifestation of R. akari.

A

Rickettsialpox

Phase 1: Firm red papule at bite site that progresses to a vesicle and then a black eschar
Phase 2: high fever, severe headache, chills/sweats, myalgias, photophobia, papulovesicular rash

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20
Q

How is R. akari treated?

A

It’s not - self-limiting

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21
Q

Describe the epidemiology of R. prowazekii.

A
  1. Found in Central/South America, Africa, and sporadically in the eastern US
  2. Seen in unsanitary conditions
  3. Peaks in the winter
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22
Q

What is the vector for R. prowazekii?

A

Human body louse (in the feces of the lice); NOT transovarian

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23
Q

What is the reservoir for R. prowazekii?

A

Humans and flying squirrels

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24
Q

What is the clinical manifestation of R. prowazekii?

A

Epidemic typhus (Louse-born typhus fever)

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25
Describe the clinical manifestation of R. prowazekii.
1. Non-specific symptoms beginning 8 days post-exposure. 1-3 days later, high fever, severe headache, myalgias 2. Petechial or macular rash (trunk, then extremities) 3. Pneumonia, athralagia, neurologic
26
What is relapse epidemic typhus called?
Recrudescent typhus or Brill-Zinsser
27
How is R. prowazekii diagnosed?
1. Symptoms/epidemiology | 2. MIF
28
How is R. prowazekii treated?
Doxycycline
29
Describe the epidemiology of R. typhi.
1. Found in warm, humid places 2. Africa, Asia, Australia, Europe, South America, TX, CA 3. 50-100 cases in the U.S. annually
30
How is R. typhi transmitted?
Rat/cat flea
31
What is the reservoir for R. typhi?
Rodents
32
What is the clinical manifestation of R. typhi?
Murine (endemic) typhus
33
Describe the clinical manifestation of R. typhi.
1-2 week incubation period | Abrupt fever, severe headache, chills, myalgia, nausea, late appearing maculopapular rash on the trunk in 50% of cases
34
How is murine typhus diagnosed?
1. Clinical features | 2. IFA
35
How is R. typhi treated?
Doxycycline
36
Discuss the epidemiology of O. tsutsugamushi.
Far East, Japan, Australi
37
What is the vector for O. tsutsugamushi?
Mites; transovarian
38
What is the reservoir for O. tsutsugamushi?
Mites
39
What is the clinical manifestation of O. tsutsugamushi?
Scrub typhus
40
Describe scrub typhus.
1. Severe headache, fever, myalgias 2. 50% get a maculopapular rash (trunk to extremities) 3. 50-80% get a necrotic eschar 4. General lymphadenopathy, splenomegaly, CNS complications, heart failure
41
What is the treatment for scrub typhus?
Doxycycline for the fever, but resolves untreated in 2-3 weeks
42
What is a macular rash?
Small, flat rash
43
What is a maculopapular rash?
Small, flat, bumpy rash
44
What is a papulovesicular rash?
Bumpy, vesicular rash with fluid inside the vesicles
45
Compare the types of rash seen in Rickettsiaecae.
1. RMSF: macular, centripetal spread (90%) 2. Rickettsialpox: papulovesicular, generalized (100%), eschar 3. Epidemic typhus: macular, centrifugal spread (20-80%) 4. Endemic typhus: maculopapular, trunk (50%) 5. Scrub typhus: maculopapular, centrifugal (<50%)
46
Describe the structure of the species within Anaplasmataceae.
1. Intracellular organisms | 2. Like a Gram negative cell wall, but no LPS or peptidoglycan
47
What are the three species associated with Anaplasmataceae?
1. Anaplasma phagocytophilum 2. Ehrlichia ewingii 3. Ehrlichi chaffeensis
48
Describe the pathogenesis of Anaplasmataceae.
Infect circulating leukocytes, RBC, platelets; replicate inside phagosome, prevent lysosomal fusion, form EBs and RBs, grow, lyse cells
49
Which species infect granulocytes? Which infect monocytes?
Granulocytes: anaplasma phagocytophilum and E. ewingii Monocytes: E. chaffeensis
50
Discuss the epidemiology of human monocyte ehrlichiosis (E. chaffeensis).
1. Vector: Lone Star tick 2. Reservoir: white-tailed deer 3. Midwest, Coastal Atlantic 4. No transovarian, most common in summer
51
Discuss the epidemiology of human anaplasmosis ehrlichiosis (E. ewingii, A. phagocytophilum).
1. Vector: Ixodes tick 2. Reservoir: small mammals 3. Upper Midwest, NE Atlantic 4. No transovarian, most common in summer
52
Describe the clinical manifestations of Anaplasmataceae.
1. Flu-like symptoms, no rash (except HME can have a late onset rash 30-40% of the time) 2. Leukopenia, thrombocytopenia, increased serum transaminases * Symptoms are disproportionate to the # of infected cells
53
How is Anaplasmataceae diagnosed?
History of tick exposure, morulae, PCR, IFA
54
How is Anaplasmataceae treated?
Doxacycline
55
Describe the structure of Coxiella burnetti.
1. GN, weak staining 2. Intracellular 3. Resistant to drying
56
What is the pathogenesis of Coxiella burnetti?
The pathogen multiples in vesicles; phagosomes fuse with endosomes to generate a low pH environment for growth, lysosome fusion is delayed
57
How does Phase I or C. burnettii differ from Phase II?
Phase I: intact LPS | Phase II: O of LPS is missing
58
Where is C. burnettii found?
Worldwide
59
How is C. burnettii transmitted?
Animals (mammalian reservoirs) to humans by inhalation of dust
60
What is the clinical manifestation of C. burnettii?
Q-fever
61
Describe Q-fever.
No rash, mild/dry/hacking cough, flu-like Chronic Q-fever: subacute endocarditis
62
How is Q-fever diagnosed?
Serology (see phase II Ag in acute illness, see both Ag in chronic illness)
63
How is Q-fever treated?
Doxycycline

MHD 1 (58 decks)

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