What is the morphology of rickettsia?
small, rod shaped, obligate IC
Where do Rickettsiae multiply?
endothelial cells of BVs: endothelial proliferation and perivascualr inflitration
What is the pathogenesis of Rickettsiae?
attaches to surface>induces phagocytosis>leaves lysosome and enters cytoplasm>accumulates>cell lysis
How is RMSF transmitted?
lower animals>wood tick/dog tick>humans in Eastern & SE US
How is Rickettsiae diagnosed?
PCR-based assays
serological testing: complement, indirect immuno, latex agglut
Weil-Felix rnx
How is Rickettsiae treated?
Doxycycline, tetracycline, erythromycin
(penicillins are ineffective; sulfonamides increase the severity of infection)
What is the clinical presentation of RMSF?
headache, fever, malaise, chills then macular>petechial rash (2-4 days later) on trunk, soles/palsms
What are complications of RMSF?
DIC, thrombocytopenia, encephalitis, vasc collapse, renal & cardiac failure
How is R. akari (Rickettsial Pox) transmitted?
house mouse>house mouse mite> people of large urban areas of US, Russia, Korea
What is the clinical presentation of R. akari?
Rickettsial Pox: vesicular rash, loacl eschar, regional lymphadenopathy, erythematous papules>vesicles>eschar
chills, fever, malaise, headache, myalgia
How is epidemic typhus (R. Porawzekii) spread?
human/flying squirrel>human body louse or head louse> people in central & south america, africa, crowded/poor hygiene conditions
What is Brill-Zinsser Disease?
a mild relapse of epidemic typhus, 10-40 years later
What is the clinical presentation of epidemic typhus?
headache, malaise and fever 1-2 weeks after infection
rash after 4-7 days: patchy, cutaneous erythema >maculopap, petechial or hemorrhage
spreads from trunk to extremeities
What are the complications of epidemic typhus?
CNS dysfnx
Brill-Zinsser Disease
How is endemic typhus (R. typhi) spread?
rat>rat flea> SE & Gulf Coast (of US)
What is the clinical presentation of endemic typhus?
abrupt onset of fever, headache, malaise, myalgia, skin rash: trunk > extremities
fatalities in the elderly/sick
How is Scrub Typhus (orientia tsutsugamushi) spread?
rodents>mites>vertebrates in Japan, Australia, India, Vietnam, Korea
What is the clinical presentation of scrub typhus (orientia tsutsugamushi)?
chills, fever, headache 3 weeks after bite
local cutaenous rash>vesicular>eschar
30% mortality if untreated
How is erlichiosis spread?
cattle/domestic animals/dogs>deer tick/dog tick>people in SE, mid-atlantic, south and central US
What is the clinical presentation of Erlichiosis?
fever, headache, malaise and myalgia 10-12 days after bite
mortality most common in the elderly
What is the morphology of Yersinia Pestis?
short, gram (-) rods
Wright-Giemsa Stain: bipolar/safety pin staining
What is the pathogenesis of y pestis?
facultative IC
capsular & cell wall Ags provide resistance to phagocytosis
type III secretion system: antiphagocytic, anti-inflamm, and toxic proteins
How is Y. Pestis transmitted?
rodents/small mammals>fleas>humans

humans get it from contact w/rodents, biet of flea, resp transmission from man-man

What are the 2 cycles of Y. Pestis?
1. sylvatic: bubonic
2. urban: pneumonic
What are the complications of Y. Pestis?
septicemia: lungs, liver, spleen, meninges
pneumonic: hemorrhagic consolidation, sepsis, death
How is Y. Pestis treated?
streptomycin, gentamicin
What is the morphology of Francisella Tularemia?
small, facultative, gram (-) coccobacillus
What is the pathogenesis of Francisella Tularenis?
encapsulated (resists intraphagocytic killing), macrophages>necrosis>granulomas
How are humans infected w/francisella tularensis (rabbit fever)?
direct contact w/animal, bite of vector, aerosol inhalation, ingestion of contaminated food/h20
What animals are a resevoir for francisella tularensis?
rabbits, squirrels, muskrats, beavers, deer
What are the types of Tularemia?
oculoglandur: painful, purulent conjuctivitis; cervical/preauricular lymphadenopathy
typhoidal: most severe; bacteremia to lung, liver, kidney, spleen; fever, weight loss, PNA
ulceroglandular: most common; ulcerating, necrotic papule w/in 2-6 days
glandular: regional LN elnargment, fever, headache, malaise w/absecense of skin lesion
How is tularemia diagnosed and treated?
Dx: serology: agglutination in 2-4 weeks
Tx: streptomycin or gentamicin for 7-10 days
attenuated vaccine for people at risk
morphology of brucella
short, gram (-) rods
catalase (+)
oxidase (+)
complex media: trypticase-soy agar, CO2
What are the routes of infection for brucella?
intestinal tract, mucous membranes, skin
(enter and multiply in phagocyte; spread through lymph>LNs>bloodstream>organs/tissues)
What is the clinical presentation of Brucella?
insidious onset of malaise, fever, weakness, aches, sweats
undulant fever w/diurnal variation
enlarged LNs & palpable spleen
What is seen microscopically with Brucella?
granulomatous nodules & abscesses in lymph, spleen, kidney, BM
epitheloid & giant cells
central necrosis
periph fibrosis
What are the chronic symptoms of Brucella?
low grade fever, weight loss, myalgia, nervousness
How is brucella treated?
combination of tetracycline w/streptomycin or gentamycin for 4-6 weeks
pasteurella multocida
small, gram (-) coccobacilli
non-hemolytic mucoid colonies
normal flora of resp & GI tract of various animals
What is a common cause of infection following bite/scratch of cat or dog?
paterurell multicoda
What is the clinical presentation of pasteurella multocida?
diffuse cellulitis w/well-defined erythematous border
chronic abscess may develop
diffuse cellulitis w/well-defined erythematous border
pasteurella multocida
Categories: Microbiology