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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
Q

Describe the clinical manifestation of R. prowazekii.

A
  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
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26
Q

What is relapse epidemic typhus called?

A

Recrudescent typhus or Brill-Zinsser

27
Q

How is R. prowazekii diagnosed?

A
  1. Symptoms/epidemiology

2. MIF

28
Q

How is R. prowazekii treated?

A

Doxycycline

29
Q

Describe the epidemiology of R. typhi.

A
  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
Q

How is R. typhi transmitted?

A

Rat/cat flea

31
Q

What is the reservoir for R. typhi?

32
Q

What is the clinical manifestation of R. typhi?

A

Murine (endemic) typhus

33
Q

Describe the clinical manifestation of R. typhi.

A

1-2 week incubation period

Abrupt fever, severe headache, chills, myalgia, nausea, late appearing maculopapular rash on the trunk in 50% of cases

34
Q

How is murine typhus diagnosed?

A
  1. Clinical features

2. IFA

35
Q

How is R. typhi treated?

A

Doxycycline

36
Q

Discuss the epidemiology of O. tsutsugamushi.

A

Far East, Japan, Australi

37
Q

What is the vector for O. tsutsugamushi?

A

Mites; transovarian

38
Q

What is the reservoir for O. tsutsugamushi?

39
Q

What is the clinical manifestation of O. tsutsugamushi?

A

Scrub typhus

40
Q

Describe scrub typhus.

A
  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
Q

What is the treatment for scrub typhus?

A

Doxycycline for the fever, but resolves untreated in 2-3 weeks

42
Q

What is a macular rash?

A

Small, flat rash

43
Q

What is a maculopapular rash?

A

Small, flat, bumpy rash

44
Q

What is a papulovesicular rash?

A

Bumpy, vesicular rash with fluid inside the vesicles

45
Q

Compare the types of rash seen in Rickettsiaecae.

A
  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
Q

Describe the structure of the species within Anaplasmataceae.

A
  1. Intracellular organisms

2. Like a Gram negative cell wall, but no LPS or peptidoglycan

47
Q

What are the three species associated with Anaplasmataceae?

A
  1. Anaplasma phagocytophilum
  2. Ehrlichia ewingii
  3. Ehrlichi chaffeensis
48
Q

Describe the pathogenesis of Anaplasmataceae.

A

Infect circulating leukocytes, RBC, platelets; replicate inside phagosome, prevent lysosomal fusion, form EBs and RBs, grow, lyse cells

49
Q

Which species infect granulocytes? Which infect monocytes?

A

Granulocytes: anaplasma phagocytophilum and E. ewingii

Monocytes: E. chaffeensis

50
Q

Discuss the epidemiology of human monocyte ehrlichiosis (E. chaffeensis).

A
  1. Vector: Lone Star tick
  2. Reservoir: white-tailed deer
  3. Midwest, Coastal Atlantic
  4. No transovarian, most common in summer
51
Q

Discuss the epidemiology of human anaplasmosis ehrlichiosis (E. ewingii, A. phagocytophilum).

A
  1. Vector: Ixodes tick
  2. Reservoir: small mammals
  3. Upper Midwest, NE Atlantic
  4. No transovarian, most common in summer
52
Q

Describe the clinical manifestations of Anaplasmataceae.

A
  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
Q

How is Anaplasmataceae diagnosed?

A

History of tick exposure, morulae, PCR, IFA

54
Q

How is Anaplasmataceae treated?

A

Doxacycline

55
Q

Describe the structure of Coxiella burnetti.

A
  1. GN, weak staining
  2. Intracellular
  3. Resistant to drying
56
Q

What is the pathogenesis of Coxiella burnetti?

A

The pathogen multiples in vesicles; phagosomes fuse with endosomes to generate a low pH environment for growth, lysosome fusion is delayed

57
Q

How does Phase I or C. burnettii differ from Phase II?

A

Phase I: intact LPS

Phase II: O of LPS is missing

58
Q

Where is C. burnettii found?

59
Q

How is C. burnettii transmitted?

A

Animals (mammalian reservoirs) to humans by inhalation of dust

60
Q

What is the clinical manifestation of C. burnettii?

61
Q

Describe Q-fever.

A

No rash, mild/dry/hacking cough, flu-like

Chronic Q-fever: subacute endocarditis

62
Q

How is Q-fever diagnosed?

A

Serology (see phase II Ag in acute illness, see both Ag in chronic illness)

63
Q

How is Q-fever treated?

A

Doxycycline

MHD 1 (58 decks)

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