Rickettsia Flashcards
rickettsia sp overview
*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
rickettsia life cycle
*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)
overview of tickborne infections
*potentially severe, life-threatening disease
*difficult and elusive diagnosis (misdiagnosis common) (early presentation is nonspecific)
*treatment inexpensive and widely available (doxycycline)
pathogen that causes Rocky Mountain Spotted Fever
Rickettsia rickettsii
vectors for Rocky Mountain Spotted Fever
*dermacentor variabilis (dog tick)
*dermacentor andersoni (wood tick)
organism that causes tyhpus
Rickettsia prowazekii
vector for typhus
lice; flying squirrels
Rocky Mountain Spotted Fever - pathogenesis
*infects vascular endothelium and smooth muscle, causing SMALL VESSEL VASCULITIS
*inflammation due to LPS and peptidoglycan
*subsequent host lyphohistiocytic response
Rocky Mountain Spotted Fever - clinical presentation
*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
Rocky Mountain Spotted Fever - complications
-meningitis
-myocarditis
-septic shock/DIC
which 2 diseases that we discussed present with a rash that involves the palms and soles
1) syphilis (secondary)
2) rocky mountain spotted fever
Rocky Mountain Spotted Fever - diagnosis
SEROLOGIC (latex agglutination test)
*need a high degree of suspicion to test for it
human granulocyte anaplasmosis (HGA) - vector
Ixodes scapularis (same as lyme disease)
human granulocyte anaplasmosis (HGA) - overview
*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
human monocytic ehrlichiosis (HME) - vector
lonestar tick
human monocytic ehrlichiosis (HME) - pathogens
*Ehrlichia chaffeensis
*Ehrlchia ewingii
human monocytic ehrlichiosis (HME) - overview
*small, gram negative bacteria
*primarily infect MONOCYTES
*much more severe in patients without a SPLEEN
Rickettsia parkeri
*mild RMSF-like illness
*sparse, vesiculopapular rash
*tick-bite ESCHAR (eschar is a clue of R. parkeri)
*common in southeast US
typhus (Rickettsia prowazekii) - clinical presentation
*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
treatment for rickettsia and rickettsia-like diseases
doxycycline
