Term
| How do Rickettsia infect humans? |
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Definition
| Infect endothelial cells by stimulating phagocytosis- they degrade the phagosome and enter the cytoplasm- OBLIGATE INTRACELLULAR |
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Term
| What is the main virulence factor of Rickettsia? |
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Definition
Phospholipase A- degrades the phagosome;
progeny can enter neighboring cells without going extracellular |
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Term
| What causes Rocky Mountain Spotted Fever and what is its vector? |
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Definition
| R. rickettsii; Rocky mountain wood tick or dog tick (found in South Eastern US) |
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Term
| What are the clinical manifestations of RMSF? |
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Definition
Abrupt onset of fever, chills, headache, myalgia (after tick bite;
Rash 2-3 days later |
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Term
| What is distinctive about the rash in RMSF? |
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Definition
The rash BEGINS on HANDS AND FEET and SPREADS INWARDS;
starts as a macular rash but in late stages is petechial and hemorrhagic |
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Term
|
Definition
| Giemsa stain; fluorescent Ab staining; Weil-felix (non-specific and insensitive) |
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Term
| What is distinctive about administering treatment in RMSF? |
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Definition
| "Treat first and ask questions later" CDC recommends commencing treatment at first suspicion, since morbidity and mortality increase if treatment is delayed |
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Term
| What causes Rickettsialpox, and where is it most likely to be encountered? |
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Definition
| Rickettsia akari- urban infection spread from mice to people via MOUSE MITES |
|
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Term
| What are the symptoms of Rickettsialpox? |
|
Definition
Local skin proliferatio-
3-7 days- firm red papules; flu-like illness with SWEATING AND PHOTOPHOBIA, cough, vertigo, rhinorrhea, nausea, vomiting
2-3 days later- papulovesicular rash, 2-40 lesions on palms and soles |
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Term
| What is the organism that causes Epidemic Typhus and how is it transmitted to humans? |
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Definition
| R. prowazekii, human body lice |
|
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Term
| What are the typical living conditions in which you would find epidemic Typhus? |
|
Definition
| Crowded unsanitary conditions |
|
|
Term
| What is the reservoir for Epidemic Typhus? |
|
Definition
| Flying Squirrels and their feces |
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Term
| What are the clinical manifestations of Epidemic Typhus? |
|
Definition
Fever, chills, headache, myalgia after 8 days;
7 days later a maculopapular rash appears on the trunk and spreads to the extremities;
Can cause Brill-Zinsser disease decades after initial infection |
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Term
| What is distinctive about the rash from Epidemic Typhus? |
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Definition
| It starts on the TRUNK and SPREADS TO EXTREMITIES |
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Term
| What bug causes Brill-Zinsser Disease? |
|
Definition
| R. Prowazekii (Epidemic Typhus) |
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Term
| What organism causes Endemic Typhus and what vector transmits it? |
|
Definition
|
|
Term
| What are the symptoms of Endemic (Murine) Typhus? |
|
Definition
| fever, chills, headache, myalgia, sometimes a rash |
|
|
Term
| How is Endemic Typhus diagnosed? |
|
Definition
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Term
| What organism causes Scrub Typhus, and what vector transmits it? |
|
Definition
| Rickettsia tsutsugamushi, chiggers (mite larvae) ASIA, AUSTRALIA, PACIFIC ISLANDS |
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|
Term
| What are the symptoms of Scrub Typhus? |
|
Definition
| Fever, chills, headache, myalgia- maculopapular rash with centrifugal spread |
|
|
Term
| What two Rickettsia infections involve a rash that spreads centrifugally from trunk to extremities? |
|
Definition
| Epidemic Typhus and Scrub Typhus |
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Term
| What organism causes Ehrlichiosis and what vector transmits it? |
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Definition
| Ehrlichia chaffeensis, Ehrlichia ewingii; black-legged tick (deer tick), lonestar tick |
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|
Term
| What causes human monocytic ehrlichiosis (HME)? |
|
Definition
|
|
Term
| What causes human granulocytic ehrlichiosis (HGE)? |
|
Definition
|
|
Term
| What causes human granulocytic anaplasmosis (HGA)? |
|
Definition
| Anaplasma phagocytophilum |
|
|
Term
| What cells are infected in each of the types of Ehrlichiosis? |
|
Definition
HGA- neutrophils;
HME- monocytes |
|
|
Term
|
Definition
| Ehrlichia invades a leukocyte by phagocytosis and multiplies within the phagosome- this is now an inclusion body containing the organisms which is called a Morula- it later lyses and spreads |
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|
Term
| What are the symptoms of Ehrlichiosis (common between all types)? |
|
Definition
flu-like symptoms, nausea, vomiting, abdominal pain;
in severe cases it can manifest like RMSF and be lethal |
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|
Term
| How is Ehrlichiosis diagnosed? |
|
Definition
Serological Testing (IFA);
Wright-stained blood smears-
VISIBLE MORULAE |
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Term
| What is the organism that causes Q fever and how is it spread? |
|
Definition
| Coxiella burnetti, spread via inhalation in areas that contain goats, sheep, cattle, and cats |
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|
Term
| If you were making a microbiology exam and you wanted to test on Q fever, what OCCUPATIONS would you mention for the patients in your clinical scenario? |
|
Definition
| Farmers, Veterinarians, Butchers |
|
|
Term
| Where are some places that Coxiella burnetii can be found? |
|
Definition
| Placenta and feces of infected livestock; NON-PASTEURIZED MILK; contaminated wool or hides |
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Term
| What is unique about the immunopathogenesis of Q fever? |
|
Definition
ANTIGENIC VARIATION OF LPS-( it is gram negative)-
LPS has a complex carbohydrate that blocks antibody binding PHASE I ANTIGEN
This mutates to PHASE II antigen which exposes Ab binding sites |
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|
Term
| How is Ab response used to diagnose acute vs. chronic Q fever? |
|
Definition
Acute disease- Ab against PHASE II ANTIGEN ONLY
Chronic disease- High Ab titers against both PHASE I and PHASE II ANTIGENS |
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|
Term
| What are the clinical manifestations of Q Fever? |
|
Definition
Acute: Fever, flu-like illness, cough, SOB, chest pain- looks like atypical pneumonia-; myocarditis; hepatitis; headache; confusion; neck stiffness
Chronic: Subacute ENDOCARDITIS WITH NEGATIVE CULTURES- fever, fatigue, dyspnea, and rash (from septic thromboembolism) |
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