L10 MHD: Rickettsia Flashcards
1
Q
Name the Disease associated with the organism
- Rickettsia Rickettsii
- R. Akari
- R. Prowazekii
- R. Typhi
- E. Chaffeensis
- A. Phagocytophilum, E. Ewingii
- Coxiella Burnetii
A
- Rocky Mountain Spotted Fever**
- Rickettsialpox
- Epidemic Typhus (spread by human body louse)**
- Murine Typhus (spread by fleas)
- Ehrlichiosis (HME human monocyte)**
- Ehrlichiosis (HA Human aniplasmosis)**
- Q Fever
** denotes organisms marked as important on the slide
2
Q
General Characteristics of Rickettsia
- Gram test?
- Motility?
- What type of parasite?
- All require an arthropod vector except which?
- Most Rickettsia cause what symptoms?
- You can treat all forms of Rickettsia with what abx?
- How does division occur? Is growth slow or fast?
A
- Small, gram negative rods
* *Don’t really use the gram stain to see them- use Giemsa stain where Rickettsia stains bluish/purple** - Non-motile (no flagella)
- Obligate intracellular parasite (steal host ATP)
- All require arthropod except Q Fever (Coxiella Burnetti)
- Most cause severe headache, rashes, and high fever
- Doxycycline
- Binary fission, slow growth (8-10 hours)
3
Q
Pathogenesis
1. Bacteria enter by ______________, which requires _______
- Once inside host, bacteria can replicate in what two locations?
- Where do the following replicate: Orienta, Rickettsia, Ehrlichia, Anaplasma, Coxiella?
A
- Bacteria enter by endocytosis (requires energy)
- Replicate in
- The cytoplasm: Rickettsia, Orientia
- Membrane bound cytoplasmic vesicle:
- -Phagosome: Ehrlichia, Anaplasma
- -Phagolysosome-like vesicle: Coxiella
4
Q
Pathogenesis of Ehrlichia & Anaplasma:
- Where do they replicate?
- How do they prevent their own degradation?
A
- Replicate in phagosome
- Prevent their own degradation by preventing phagosome/lysosome fusion
* *If they two fuse, the organisms are killed**
5
Q
Pathogenesis of Coxiella
- Where does it replicate?
- What is required for growth?
A
- replicates in CCV- Coxiella containing vesicle -phagosome fuses with endosome! (phagolysosome-like)
- low pH is required for growth
6
Q
- Where do R. Rickettsii, R. Typhi and Orienta replicate?
2. How do R. Rickettsia and R. Typhi migrate?
A
- Replicate/multiply freely in the cytoplasm
- R. Rickettsii and R. Typhi (fleas) migrate intracellularly using actin polymerization- polymerize actin at pole, pushes bacteria across cytoplasm- organisms can encounter host cell membrane.
7
Q
- What strain of R. Typhus is transmitted by a human body louse (epidemic)?
- Does it use actin polymerization to migrate intracellularly?
- How does it exit the host?
A
- R. Prowazekii
- Does not use actin polymerization! (R. Typhi- flea- endemic strain does!)
- Exits host via lysis- keeps growing until they lyse the host cell
* *R. Rickettsia & R. Typhi exit by budding**
8
Q
How do R. Rickettsii, R. Typhi and Orientia escape the phagosome?
A
Use phospholipase A
9
Q
- How do Rickettsia, Orientia, Ehrlichia, and Anaplasma fair outside of the cell?
- How is Coxiella different?
A
- They are unstable and die rapidly- they require CoA & NAD+
- Coxiella remains viable for years- it’s resistant to dying
10
Q
What diseases are spread by the following insect vectors:
- Ticks
- Mites
- Lice
- Fleas
What diseases have the following animal reservoirs?
- Rodents
- Dogs
- Flying Squirrels
- Deer
A
VECTORS:
- Ticks
- RMSF
- Ehrlichiosis - Mites
- Rickettsialpox
- Scrub Typhus - Lice
- Epidemic Typhus (R. Prowazekki) - Fleas
- Murine Typhus (R. Typhi)
RESERVIORS:
- Rodents
- RMSF
- Rickettsialpox
- Murine Typhus
- Ehrlichiosis- HA - Dogs:
- RMSF - Flying Squirrels:
- Epidemic Typhis (R. Prowazekki) - Deer
- Ehrlichiosis- HME
11
Q
- How do R. Ricksettii & R. Typhus cause rash?
2. Where do the rashes form?
A
- Bacteria multiply in endothelial cells lining small blood vessels- rupture results in rash
- Primary lesion: vasculitis in many organs (prominent in the skin) - R. Rickettsii causes a rash that typically starts at wrists and ankles and then spreads to the trunks, palms, and soles
- R. Typhus produces a rash that starts out centrally and spreads out, sparing the palms and soles
“Rickettsii on wRists, Typhus on the Trunk “
12
Q
Diagnosis is based on which two of the following:
a) clinical findings
b) epidemiological findings
c) serological findings
d) PCR
A
Based on clinical findings and epidemiologic information
because culturing is difficult, hazardous (obligate intracellular pathogens)
13
Q
What serological tests can be used and why do we use them?
A
Serologic tests: used to confirm the diagnosis
- Immunofluorescence assay (IFA) : Relatively sensitive, Requires little antigen, detects IgM and IgG
- Microfluorescence assay (MIF): tests for antibodies against multiple antigens
PCR is another test that can also be used for diagnosis (uncommon)
14
Q
- Do you treat patient before or after you get the results of a serology test?
- What type of therapy is this?
- What is the best antibiotic to give patients?
- Which are contraindicated?
- Is a vaccine available?
A
- Therapy before seroconversion because the more therapy is delayed, the less effective it is
- Empiric therapy
- Tetracyclines (Doxycycline) & Chloramphenicol
- Sulfonamides are contraindicated! TEST
* *R. Rickettsii is resistant to sulfa drugs - Limited vaccines available
15
Q
RMSF- Rocky Mountain Spotted Fever
- Causative agent? How long is the incubation period?
- Symptoms? Which is most important?
- Most common vector?
- Two common reservoirs?
- Where in the US is it most common?
A
- R. Rickettsii (intracellular, replicates freely in the cytoplasm, spreads via actin polymerization, most common Rickettsial pathogen in the US)
- Usual incubation period is 2-7 days but could be upwards to 2 weeks - RASH ON EXTREMITIES TEST is the most important symptom; patients also present with severe headache and high fever
- “Macular rash, initially involving the extremities” TEST - Hard Tick Vectors most common
- Associated with exposure to wooded areas where ticks exist - Common reservoirs: rodents and dogs
- Southeast Atlantic and South Central States
- More common in the summer
