Rickettsia

Question 1

General Features

Answer 1

• Very small rods/coccobacilli bacteria
• Cell wall resembles-Gram (-) stains poorly
• Giemsa stain & light microscope-Best choice
• Obligate intracellular pathogens:
• Depend on host cell for metab
• Can act as energy parasite-Uses ATP made by host
• Cell culture (cultivated)-Egg yolk or experimental animal
• Transmitted by arthropods, ticks, mites, body lice
  
  • EXCEPTION Coxiella (Q fever)

Question 2

Rickettsia (general)

Answer 2

• Cell wall stains poorly & little endotoxicity
• Obligate intracellular pathogen of endo cells
• Share antigen w/proteus sp (weil-flex test)
• 2 groups-
• Spotted fever-17 species
  
  • _{^{R. akari & rickettsii in North America}}
• Typhus-R. Prowazekii & R. typhi
• Transmission: animal & arthropod (tick, mites, fleas)
• Transovarian transmission-Human an accidental host

Question 3

Rickettsia (Clinical)

Answer 3

• Pathogenesis: Multiply in vascular (small arteries) endothelial cells-Through phagocytosis
  
  • _{^{Allows for phagosome escape multiply in cytoplasm}}
• Mode of exit:
• Lysis (prowazekii)
• Focal lysis _^(ricketsii)-Rearranges actin filaments for propulsion=Filopodia _{^{(Host F-actin help push it out)}}
• Presentation: Vasculitis, thrombosis w/generalized distrubution in the body (skin-rash)
  
  • _{^{<strong>Heart, lungs, kidney</strong>}}
  • MAJOR damage due to leakage of blood/tissue damage
• Treatment: Tetracycline, cholramphenical
• **Never Sulfonamides=promote growth **

Question 4

R. Ricketsii (general)

Answer 4

• Rocky mountain spotted fever
• Most common disease in US SouthEastern states
• Found in wild rodents, dogs-_Vector is Ticks_ _{^{(exposed 6hrs +)}}
• High risk: Hunters, hikers, campers
  
  • _{^{Pesticide does NOT kills eggs (repeated monthly)}}
• 2-14 day incubation period-Rapid onset of symptoms
• Triad-Fever, headache, rash
• Wide spread vasculitis=GI symptoms, CNS confusion, Stiff neck, conjunctivits
• Severe cases-DIC, encephalitis, resp, renal & cardiac failure
• Rash develops on 3rd day-Maculopapular progress to petechial
• _{^{Presents <em><strong>1st on ankles & wrist + swelling</strong></em> spreads to trunk, palms, soles->gangrenous}}
• Death @ day 8-15

Question 5

R. Ricketsii (clinical)

Answer 5

• Diagnosis: Antigen detection-Direct fluores skin lesion biopsy
• Serology-Ab detection
• Indirect fluorescent detect Abs in pts sera
• Weil-Felix test-Agglutination using Proteus Ags
  
  • _{^{Cross-reacting Ags}}
• Treat: Early agressive treatment-Doxycycline
  
  • _{^{Can also be used as prophylaxis}}
  • _{^{Risk for pregers & children under 8, BUT STILL GIVEN}}
• Sulfo-CONTRAINDICATED

Question 6

Ricketissial Pox (R.akari)

Answer 6

• Urban distrubution (NYC)
• Found in mice & mites _{^{(Transoverian-infected female mite eggs)}}
• Disease: Papule w/necrotic eschar _{^{(Anthrax like)}} @ Bite site
• Later fever, myalgia, chills, **RASH w/vesicles dry & crust over **
• Treat: Mild presentation due to spontaneous healing
  
  • _{^{<strong>Doxycycline optional</strong>}}

Question 7

R. Prowazekii (Typhus)

Answer 7

• Epidemic Typhus-Worldwide sporadic cases
• Found in humans-Body lice (pediculus humanus)
  
  • NO transovarial transmission
• Transmission-_{^{scratching bite, rubbing feces into wound}}
• High risk: Crowded unsanitary cond
• War, famine, poverty-HOMELESS people
  
  • _{^{Rural Eastern states <u>assoc with squirrels</u>}}
• Diagnosis: Detection w/DFA on biopsy
• Treat: Tetracycline/Doxycycline
• Inactivated Typhus vaccine-People @ risk

Question 8

R. Prowazekii (Typhus-disease)

Answer 8

• Epidemic Typhus _{^{(“camp fever” or louse-borne thypus)}}
• IP-8 days
• Sustained high fever, severe headache, myalgias
• Macular rash on chest-5 days later fever w/spread to trunk & extermities (petechial)-_{^{Severe cases=gangrene}}
• _{^{SEVERE muscle pain, chills, <u>hypotensive (DIC),</u> Photosensitivity, & delirium}}
• Hypotensive-DIC leads to _SHOCK t_o due volume loss of circulating blood
• Brill-Zinner disease: Form of recurrent disease from reactivation of latent disease (WW2)=Served as reservoir for humans

Question 9

R. typhi (Murine)

Answer 9

• Endemic-worldwide__{^{<strong> (warm/humid) </strong>}}_Gulf states
• Found in rodents-Vector Rat flea _{^{(xenopsylla cheopis)}}
  
  • _{^{Pt will scratch feces into skin<span></span>}}
• Symptoms: Similar to epidemic typhus BUT milder with or w/o rash
• Diagnose: Indirect fluores lvl of Ab
• Treat: Tetracycline

Question 10

Scrub Typhus (Orientia Tsutsugamushi)

Answer 10

• Found in Asia, Japan, Australia
• Reservior: Rodents-Vector: Mites (transoverian)
• Disease-Scrub Typhus
• Fever, head ache, myalgias (muscle pains)
• Initial lesion=_{^{<u><strong>Necrotic eschar </strong></u><strong>@ site of bite & macupapular rash</strong>}}
• Starts @ trunk & spreads to extremities
• Lymphadenopathy, splenomegaly, CNS
• Treat: Doxycycline

Question 11

Anaplasmataceae (general)

Answer 11

• Obligate intracellular bacteria-Survive cytoplasmic vacuoles of granulocytes/monocytes (WBCs)
• Intracellular growth protection from immune
• Cell wall=Gram (-) BUT lack peptidoglycan/LPS
• Transmitted by ticks BUT NO transoverian transmission
• Pathogen multiplys in Phagosome=Phagosome-lysosome fusion inhibited
• Morulae=_{^{Intracytoplasmic inclusion body}}

Question 12

Anaplasmataceae (Ehrlichia Chaffeensis)

Answer 12

• Reservoirs: Deer, dogs & transmitted by ticks
• Geo distrubution: Worldwide in US SouthEast
• Disease: infects monocytes_{<strong> ^(WBCs) </strong>}& Macrophages
• “Human monocytic ehrlichiosis”
• IP-1 to 3 weeks flu-like symptoms fever
• Rashs develops in 30-40% of casses
• Leukopenia & Thrombocytopenia

Question 13

Anaplasmataceae (Phagocytophilum)

Answer 13

• Reservoirs: Small rodents, deer, sheeps
• Transmitted by Ticks (Ixodes spp)
• Found worldwide-US everywhere except west coast
• Disease-Infects granulocytes:
  
  • _{^{Neutrophils, eosinophils, basophils}}
• Human Granilocytic anaplasmosis
• IP=5-11 days symptoms similar to Ehrilichosis
• Diagnosis BOTH Ehrlichia & Phagocyto-
• Presence of cytoplasmic inclusion bodies=MORULAE
• Treat: Doxycylcine

Question 14

Coxiella Burnetii

Answer 14

• Gram (-) rod related to legionella
• Reservoirs: Wide range animals, birds
• Farm animal main source for human infection
  
  • _{^{<em><strong>High conc-in placenta</strong></em>, excreted in milk, urine & feces}}
• Transmission: Inhalation of airborne particles OR ingestion of unpaseurized milk/meat
• High risk-Farmers, ranchers, vets, abattoir worker
• Intracellular pathogen-monocytes & macophages
  
  • _{^{<strong>Causes diffuse granuloma w/involved organs</strong>}}
• Disease-Q fever-_{^{<strong>NO rash</strong>}}, Atypical pneumonia, hepatitis
• Chronic=Subacute endocarditis-months to years
  
  • _{^{Can be superimposed on previous valve lesions}}