Small gram negative rod that stains poorly and grows well on cysteine-enriched media? What diseases are caused by this bacteria?
Francisella tularensis: rabbit fever, tularemia and glandular fever.
Route of transmission of francisella tularensis
HIGHLY INFECTIOUS: arthropod bite (esp hard tick), mucous membrane exposure, aerosol and ingestion.
High risk groups for tularemia
Hunters, vets and lab workers
How is francisella tularensis identified?
Immunofluorescent assay, note that it grows inside of macrophages.
Spectrum of disease caused by francisella tularensis?
Primary infection: ulceroglandular (shown below), oculoglandular w/lymphadenopathy. Secondary infection: pneumonia (30% fatality), typhoidal (ingestion)
Lab diagnosis of tularemia
#1) Serology. #2) Culture of bubos, sputum, blood, GI wash on chocolate cysteine agar and buffer charcoal yeast extract. ID confirmed with slide agglutination test.
Regions of the US with highest cases of tularemia?
Arkansas, Missouri, Kansas, Oklahoma w/greater incidence in males…lots of rabbit hunting going on here?
Primary skin infection to consider whenever you consider community acquired MRSA.
Main transmission route of brucella suis in humans
Infected milk, milk products and direct contact with infected animals. THERE IS NO ARTHROPOD VECTOR.
Where would you find brucella suis in humans after someone drank unpasteurized milk?
Brucella suis enters humans via mucous membranes, skin, ingestion or inhalation. They are then engulfed by phagocytes and taken to regional lymph nodes. They multiply within macrophages and form granulomas in the reticuloendothelial system, causing recurrent bacteremia. Note that in animals it is largely found in tissues rick in erythritol (milk, genitourinary).
Occupational exposures for brucellosis
Slaughterhouse, meat-packing, vets, lab workers, hunters (esp when hunting wild hogs, elk, bison, caribou and moose).
Regions at risk for brucellosis
Those with unpasteurized dairy products: Mediterranean basin, Latin America, Africa, Asia, Middle East.
Complications of chronic brucellosis?
UNDULANT FEVER: Reticuloendothelial organs are affected but NOT enlarged: hepatic lesions, arthritis, meningitis, endocarditis.
Bug that causes cat scratch disease? What is the vector?
Bartonella henselae from the flea
Bug that causes trench fever (5-days fever)? What is the vector?
Bartonella quintana from body louse causes febrile bacteremia. Note that humans are the reservoir.
Bug that causes Carrion’s disease? What is the vector?
Bartonella bacilliformis from the sand fly. Note that humans are the reservoir.
A 5 year old boy presents with the lymph node shown below. He has cats at home. What is the method of transmission of the bacteria that most likely caused his condition?
Bartonella henselae cause cat scratch disease with intense lymphadenopathy in an immunocompetent patient. Cats are the reservoir and can transmit it directly to humans or the cat flea can transmit it to humans.
How does bartonella henselae, bartonella quintana present in an immunocompromised patient?
Bacillary angiomatosis from endothelial colonization by bartonella that causes the endothelium to proliferate. Bartonella quintana can also cause endocarditis.
2 phases of Carrion’s disease
Bartonella bacilliformis can cause hemolytic anemia (Oroya fever) in phase I and verruga peruana in the second phase.
What type of bacteria are members of the Rickettsiaceae family? How are they spread?
Rickettsia and Orientia are obligate intracellular bacteria that are transmitted by arthropods.
Bacteria, vector and reservoir in Rocky Mountain Spotted Fever?
Bacteria: R. rickettsii. Vector: ticks. Reservoir: Ticks & rodents
Bacteria, vector and reservoir in Rickettsialpox?
Bacteria: R. akari. Vector: mites. Reservoir: mites & rodents.
Bacteria, vector and reservoir in scrub typhus?
Bacteria: O. tsutsugamushi. Vector: mites. Reservoir: mites (chiggers) and rodents. Note that this does not occur in the US, but was seen in Vietnam.
Bacteria, vector and reservoir in epidemic typhus?
Bacteria: R. prowazekii. Vector: louse. Reservoir: humans, squirrel fleas, flying squirrels. Note that this is not present in the US, but epidemic in places of war like Somalia.
Bacteria, vector and reservoir in murine endemic typhus?
Bacteria: R. typhi (R. felis may also play a role). Vector: flea. Reservoir: rodents. Note that this IS present in the US (mostly in Texas).
A patient presents with a skin rash, fever, severe headache, malaise, prostration, vomiting and hepatosplenomegaly. History reveals recent tick bite and fleas. Obligate intracellular gram negative coccobacilli that are seen with Giemsa stain. What is causing his condition?
Rocky Mountain Spotted Fever from R. rickettsii and typhus from R. typhi both proliferate in endothelial lining of small arteries, veins and capillaries causing vasculitis.
How does rickettsia spread throughout the cells of our bodies?
1st they grow freely in the cytoplasm. Then they stimulate host F actin polymerization. This propels them out of the cell or into the neighboring cell
Common vector of Rocky Mountain Spotted Fever in the west?
Dermacator andersonii (Rocky Mountain wood tick)
Common vector of Rocky Mountain Spotted Fever in the east?
Dermacator verabilis (American dog tick)
Common vector of Rocky Mountain Spotted Fever in Arizona?
Rhipicephalus sanguineus (brown dog tick)
Lesion seen at site of mite bite in a patient with rickettsialpox?
Eschar (mimics cutaneous anthrax)
In contrast to Rickettsia and Orientia that live in endothelial cells, where are Ehrlichia (HME) chaffeensis and Anaplasma (HGE) found?
These are obligate intracellular bacterial that survive in cytoplasmic vacuoles of mammalian hematopoietic cells. Note that anaplasma (HGE) is found mostly in granulocytes.
Tick found in this region?
Lone Star Tick (Amblyomma Americanum).
Vector that transmits anaplasma phagocytophilum?
Ixodes scapularis (Backlogged tick, can also transmit Borrelia burgdorferi that causes Lyme disease). Note that anaplasma is found mostly in the regions Lyme is found.
Disease caused by coxiella burnetii?
A 50 year old man presents with chills, headache, atypical pneumonia and endocarditis. He is a farmer and works with cattle, goats and sheep. Labs show a small gram negative obligate intracellular bacteria. What is causing his symptoms?
Coxiella burnetii infects humans by direct contact with livestock. Ticks play a role in animal to animal transmission.
Diseases transmitted by ticks
Lyme, HGE, HME, STARI, endemic relapsing fever, RMSF, tularemia and Q fever.
Diseases transmitted by mites
Scrub typhus and rickettsialpox
Disease transmitted by lice
Pediculus humanus humanus transmites: trench fever, epidemic typhus, epidemic relapsing fever
Diseases transmitted by fleas
Endemic murine typhus (xenopsylla spp. transmits R. typhi), bubonic plague (xenopsylla cheopis transmits yersinia pestis), tularemia and cat scratch fever.
What are some things that make ticks great vectors for disease transmission?
Soft ticks live 14+ years, resistant to environmental stresses, slow feeding, transovarian disease transmission to progeny and high reproductive potential.