Microbiology-Zoonotic Bacterial Diseases

Question 1

Small gram negative rod that stains poorly and grows well on cysteine-enriched media? What diseases are caused by this bacteria?

Answer 1

Francisella tularensis: rabbit fever, tularemia and glandular fever.

Question 2

Route of transmission of francisella tularensis

Answer 2

HIGHLY INFECTIOUS: arthropod bite (esp hard tick), mucous membrane exposure, aerosol and ingestion.

Question 3

High risk groups for tularemia

Answer 3

Hunters, vets and lab workers

Question 4

How is francisella tularensis identified?

Answer 4

Immunofluorescent assay, note that it grows inside of macrophages.

Question 5

Spectrum of disease caused by francisella tularensis?

Answer 5

Primary infection: ulceroglandular (shown below), oculoglandular w/lymphadenopathy. Secondary infection: pneumonia (30% fatality), typhoidal (ingestion)

Question 6

Lab diagnosis of tularemia

Answer 6

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.

Question 7

Regions of the US with highest cases of tularemia?

Answer 7

Arkansas, Missouri, Kansas, Oklahoma w/greater incidence in males…lots of rabbit hunting going on here?

Question 8

Primary skin infection to consider whenever you consider community acquired MRSA.

Answer 8

Tularemia

Question 9

Main transmission route of brucella suis in humans

Answer 9

Infected milk, milk products and direct contact with infected animals. THERE IS NO ARTHROPOD VECTOR.

Question 10

Where would you find brucella suis in humans after someone drank unpasteurized milk?

Answer 10

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).

Question 11

Occupational exposures for brucellosis

Answer 11

Slaughterhouse, meat-packing, vets, lab workers, hunters (esp when hunting wild hogs, elk, bison, caribou and moose).

Question 12

Regions at risk for brucellosis

Answer 12

Those with unpasteurized dairy products: Mediterranean basin, Latin America, Africa, Asia, Middle East.

Question 13

Complications of chronic brucellosis?

Answer 13

UNDULANT FEVER: Reticuloendothelial organs are affected but NOT enlarged: hepatic lesions, arthritis, meningitis, endocarditis.

Question 14

Bug that causes cat scratch disease? What is the vector?

Answer 14

Bartonella henselae from the flea

Question 15

Bug that causes trench fever (5-days fever)? What is the vector?

Answer 15

Bartonella quintana from body louse causes febrile bacteremia. Note that humans are the reservoir.

Question 16

Bug that causes Carrion’s disease? What is the vector?

Answer 16

Bartonella bacilliformis from the sand fly. Note that humans are the reservoir.

Question 17

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?

Answer 17

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.

Question 18

How does bartonella henselae, bartonella quintana present in an immunocompromised patient?

Answer 18

Bacillary angiomatosis from endothelial colonization by bartonella that causes the endothelium to proliferate. Bartonella quintana can also cause endocarditis.

Question 19

2 phases of Carrion’s disease

Answer 19

Bartonella bacilliformis can cause hemolytic anemia (Oroya fever) in phase I and verruga peruana in the second phase.

Question 20

What type of bacteria are members of the Rickettsiaceae family? How are they spread?

Answer 20

Rickettsia and Orientia are obligate intracellular bacteria that are transmitted by arthropods.

Question 21

Bacteria, vector and reservoir in Rocky Mountain Spotted Fever?

Answer 21

Bacteria: R. rickettsii. Vector: ticks. Reservoir: Ticks & rodents

Question 22

Bacteria, vector and reservoir in Rickettsialpox?

Answer 22

Bacteria: R. akari. Vector: mites. Reservoir: mites & rodents.

Question 23

Bacteria, vector and reservoir in scrub typhus?

Answer 23

Bacteria: O. tsutsugamushi. Vector: mites. Reservoir: mites (chiggers) and rodents. Note that this does not occur in the US, but was seen in Vietnam.

Question 24

Bacteria, vector and reservoir in epidemic typhus?

Answer 24

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.

Question 25

Bacteria, vector and reservoir in murine endemic typhus?

Answer 25

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).

Question 26

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?

Answer 26

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.

Question 27

How does rickettsia spread throughout the cells of our bodies?

Answer 27

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

Question 28

Common vector of Rocky Mountain Spotted Fever in the west?

Answer 28

Dermacator andersonii (Rocky Mountain wood tick)

Question 29

Common vector of Rocky Mountain Spotted Fever in the east?

Answer 29

Dermacator verabilis (American dog tick)

Question 30

Common vector of Rocky Mountain Spotted Fever in Arizona?

Answer 30

Rhipicephalus sanguineus (brown dog tick)

Question 31

Lesion seen at site of mite bite in a patient with rickettsialpox?

Answer 31

Eschar (mimics cutaneous anthrax)

Question 32

In contrast to Rickettsia and Orientia that live in endothelial cells, where are Ehrlichia (HME) chaffeensis and Anaplasma (HGE) found?

Answer 32

These are obligate intracellular bacterial that survive in cytoplasmic vacuoles of mammalian hematopoietic cells. Note that anaplasma (HGE) is found mostly in granulocytes.

Question 33

Tick found in this region?

Answer 33

Lone Star Tick (Amblyomma Americanum).

Question 34

Vector that transmits anaplasma phagocytophilum?

Answer 34

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.

Question 35

Disease caused by coxiella burnetii?

Answer 35

Q-fever.

Question 36

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?

Answer 36

Coxiella burnetii infects humans by direct contact with livestock. Ticks play a role in animal to animal transmission.

Question 37

Diseases transmitted by ticks

Answer 37

Lyme, HGE, HME, STARI, endemic relapsing fever, RMSF, tularemia and Q fever.

Question 38

Diseases transmitted by mites

Answer 38

Scrub typhus and rickettsialpox

Question 39

Disease transmitted by lice

Answer 39

Pediculus humanus humanus transmites: trench fever, epidemic typhus, epidemic relapsing fever

Question 40

Diseases transmitted by fleas

Answer 40

Endemic murine typhus (xenopsylla spp. transmits R. typhi), bubonic plague (xenopsylla cheopis transmits yersinia pestis), tularemia and cat scratch fever.

Question 41

What are some things that make ticks great vectors for disease transmission?

Answer 41

Soft ticks live 14+ years, resistant to environmental stresses, slow feeding, transovarian disease transmission to progeny and high reproductive potential.