Rickettsia

Question 1

rickettsia sp overview

Answer 1

*similar to gram negative rods
*grow only in the CYTOPLASM OF EUKARYOTIC CELLS
*has LPS (weak endotoxin activity)
*stains poorly with Gram stain; better seen with Giemsa or Gimenez stains

Question 2

rickettsia life cycle

Answer 2

*enter eukaryotic cells by attaching to host cell surface receptors and stimulating phagocytosis
*after engulfment, they degrade the phagosome to be released into the cytoplasm
*spotted fever = continuous inflammation
*typhus = cell death (more acute)

Question 3

overview of tickborne infections

Answer 3

*potentially severe, life-threatening disease
*difficult and elusive diagnosis (misdiagnosis common) (early presentation is nonspecific)
*treatment inexpensive and widely available (doxycycline)

Question 4

pathogen that causes Rocky Mountain Spotted Fever

Answer 4

Rickettsia rickettsii

Question 5

vectors for Rocky Mountain Spotted Fever

Answer 5

*dermacentor variabilis (dog tick)
*dermacentor andersoni (wood tick)

Question 6

organism that causes tyhpus

Answer 6

Rickettsia prowazekii

Question 7

vector for typhus

Answer 7

lice; flying squirrels

Question 8

Rocky Mountain Spotted Fever - pathogenesis

Answer 8

*infects vascular endothelium and smooth muscle, causing SMALL VESSEL VASCULITIS
*inflammation due to LPS and peptidoglycan
*subsequent host lyphohistiocytic response

Question 9

Rocky Mountain Spotted Fever - clinical presentation

Answer 9

*incubation period 2-14 days (median = 7)
*initial cardinal symptoms: fever, headache, myalgia (achy muscles)
*rash - PETECHIA and PURPURA, involving PALMS AND SOLES
*possibly nausea, vomiting, abdominal pain, diarrhea

Question 10

Rocky Mountain Spotted Fever - complications

Answer 10

-meningitis
-myocarditis
-septic shock/DIC

Question 11

which 2 diseases that we discussed present with a rash that involves the palms and soles

Answer 11

1) syphilis (secondary)
2) rocky mountain spotted fever

Question 12

Rocky Mountain Spotted Fever - diagnosis

Answer 12

SEROLOGIC (latex agglutination test)
*need a high degree of suspicion to test for it

Question 13

human granulocyte anaplasmosis (HGA) - vector

Answer 13

Ixodes scapularis (same as lyme disease)

Question 14

human granulocyte anaplasmosis (HGA) - overview

Answer 14

*primarily infects granulocytes (neutrophils)
*small, gram-negative bacteria
*sometimes a morula in the buffy coat
*manifestations of disease from cytokine release and SIRS
*questions usually give you someone from Connecticut

Question 15

human monocytic ehrlichiosis (HME) - vector

Answer 15

lonestar tick

Question 16

human monocytic ehrlichiosis (HME) - pathogens

Answer 16

*Ehrlichia chaffeensis
*Ehrlchia ewingii

Question 17

human monocytic ehrlichiosis (HME) - overview

Answer 17

*small, gram negative bacteria
*primarily infect MONOCYTES
*much more severe in patients without a SPLEEN

Question 18

Rickettsia parkeri

Answer 18

*mild RMSF-like illness
*sparse, vesiculopapular rash
*tick-bite ESCHAR (eschar is a clue of R. parkeri)
*common in southeast US

Question 19

typhus (Rickettsia prowazekii) - clinical presentation

Answer 19

*rash like RMSF but starts at TRUNK and moves to extremities
*presents as a severe RMSF like illness (fever, headache, myalgia)
*often with meningoencephalitis and cranial nerve defects in more sever cases
*causes cell death all at once

Question 20

treatment for rickettsia and rickettsia-like diseases

Answer 20

doxycycline