Bacterial Zoonoses

Question 1

What are the carriers of Brucella?

Answer 1

Sheep, cattle, pigs and dogs

Question 2

How do humans get brucellosis?

Answer 2

• Consume unpasteurized dairy products

* Contact with infected animals

Question 3

What populations are at high risk for brucellosis?

Answer 3

– Abattoirs (slaughterhouse workers)
– Veterinarians
– Farmers
– Lab Workers

Question 4

What Category is Brucella?

Answer 4

Category B Infectious Agent

Question 5

What is the pathogenesis of Brucella?

Answer 5

• Organisms penetrate skin or mucous membranes
• Phagocytosized by macrophages and monocytes
• Carried to spleen, liver, bone marrow, lymph nodes and kidneys
• Organisms multiply in macrophages in the reticuloendothelial system
• Host reaction is the formation of small granulomas

Question 6

What type of immunity is necessary to fight Brucella?

Answer 6

T cell immunity determines recovery

Ab are ineffective as it is intracellular

Question 7

What are the major symptoms of brucellosis?

Answer 7

• Undulant Fever (kind of like in B. recurrentis)

- Splenomegaly, lymphadenopathy, hepatomegaly

Question 8

What are the requirements for Brucella culture?

Answer 8

Requires enriched media and prolonged incubation to grow

Question 9

What does Brucella look like under the microscope?

Answer 9

Grains of sand - they are very small in size

Question 10

What is the treatment for Brucella infection?

Answer 10

Oral tetracyclines along with aminoglycosides for a prolonged time

Question 11

What is the cause of tularemia?

Answer 11

Francisella tularensis

Question 12

What is the transmission of F. tularensis?

Answer 12

Deer flies and ticks

Question 13

Does F. tularensis have ovarian transfer in ticks?

Answer 13

Yes. there is transovarial transmission in ticks

Question 14

What populations are at the greatest risk for tularemia?

Answer 14

• Hunters
• Lab workers
• People exposed to ticks

Question 15

What states in the US have high tularemia incidence?

Answer 15

Missouri
Arkansas
Oklahoma

Question 16

What are the reservoirs of tularemia?

Answer 16

Rabbits

Rodents

Question 17

What Category is F. tularensis?

Answer 17

Category A

Question 18

What is the pathogenesis of tularemia?

Answer 18

• Organisms enter through breaks in the skin or mucous membranes
• Limited number of organisms are needed for infection
• Ulcer may develop at entry site
• Organisms may disseminate via the
bloodstream
• Host response is granuloma formation

Question 19

What kind of immunity is required to fight tularemia?

Answer 19

Cellular immunity

Question 20

What are clinical manifestations of tularemia?

Answer 20

• Fever, chills, malaise 2-5 days after exposure
• Ulceroglandular infections
• Oculoglangular
• Typhoidal infection (ingestion of high number of organisms)

Question 21

How is tularemia diagnosed?

Answer 21

• Immuno-fluorescent stain of smears for rapid diagnosis

- Acute and convalescent agglutinin antibody titers over time to assess Ab reaction

Question 22

What are the requirements for F. tularensis culture?

Answer 22

• Requires sulfhydryl compounds for growth
• Requires extended incubation time
• Strict aerobe

Question 23

What is the treatment for tularemia?

Answer 23

Streptomycin, gentamicin, tetracycline or choramphenicol

Removal of ticks promptly

Question 24

What are characteristics of Pasteurella?

Answer 24

• Gram-negative, non-motile bacilli
• Facultative anaerobes
• Fermentative

Question 25

What are carriers of Pasteurella?

Answer 25

• Normal respiratory and GI flora of cats and dogs

* Associated with cat & dog bites and scratches

Question 26

What is the most common cause of pasteurellosis?

Answer 26

Cat bite

Question 27

What is the most common Pasteurella species isolated from humans?

Answer 27

Pasteurella multocida

Question 28

What are the growth requirements and characteristics of P. multocida?

Answer 28

• Grows on blood and chocolate but
not MacConkey agar
• Large buttery colonies with moth ball odor

Question 29

What is unique about P. multocida in its response to penicillin?

Answer 29

It is sensitive to penicillin even though it is Gram negative

Question 30

What is the cause of the plague?

Answer 30

Yersinia pestis

Question 31

How is the plague transmitted?

Answer 31

Fleas

Question 32

What is the Urban Plague?

Answer 32

Urban Plague-maintained in rat population and spread to humans by fleas

Question 33

What is the Sylvatic Plague?

Answer 33

Sylvatic Plague-endemic in western USA. Carried by prairie dogs, mice, rabbits, rats.

Question 34

What is the pathogenesis of the plague?

Answer 34

• Organisms multiply in the flea’s gut
• Flea bites human or another rodent
• Organisms move from bite site to lymph nodes
• Organisms multiply in lymph nodes, necrosis and swelling -> Bubo
• Organisms -> blood, lungs, liver & spleen

Question 35

What is the plague called the Black Death?

Answer 35

Terminal cyanosis of the extremities

Question 36

What states is the plague endemic to?

Answer 36

Arizona
California
Colorado
New Mexico
Oregon

Question 37

What Category is Y. pestis?

Answer 37

Category A

Question 38

What is the shape of the Y. pestis cells in culture?

Answer 38

Safety pins

Question 39

What is used to treat the plague?

Answer 39

Streptomycin

Question 40

A 6 Y.O. boy arrives with his mother in ER complaining of pain in right arm where a cat had bit him the previous day. The next morning the boy awoke crying and complaining of pain in his hand. Temp 39 C. Skin over the wound is erythematous. Material from the wound is submitted for culture and Gram stain. The laboratory reports growth of gram-negative coccobacilli. The organisms were faculatatively anaerobic but failed to grow on MacConkey agar. Which organisms is most likely responsible for this infection?

A. Capnocytophaga 
B. Eikenella
C. Escherichia
D. Fusobacterium 
E. Pasteurella

Answer 40

E. Pasteurella

Question 41

Which arthropod is the most important vector of tuleremia?

A. House fly 
B. Flea
C. Lice
D. Tsetse fly 
E. Tick

Answer 41

E. Tick

Question 42

During a military conflict in Somalia, several soldiers develop a febrile illness characterized by abrupt onset of fever with rigors, severe headaches, myalgias, arthralgias, lethargy, photophobia, and coughing. Conjunctival suffusion and a petechial rash develop 4 days into the illness and then fade after 1 to 2 days at the time symptoms wane. Splenomegally and hepatomegaly are also observed. After 1 week, the symptoms recur. Blood cultures are collected during febrile phase and are positive after extended (7 days) incubation with small, faint staining gram-negative coccobacill. What is the likely etiologic agent for this disease?

A. Brucella melitensis
B. Escherichia coli
C. Francisella tularensis
D. Haemophilus influenzae 
E. Pasteurella multocida

Answer 42

A. Brucella melitensis