Bacterial Zoonoses Flashcards
What are the carriers of Brucella?
Sheep, cattle, pigs and dogs
How do humans get brucellosis?
- Consume unpasteurized dairy products
* Contact with infected animals
What populations are at high risk for brucellosis?
– Abattoirs (slaughterhouse workers)
– Veterinarians
– Farmers
– Lab Workers
What Category is Brucella?
Category B Infectious Agent
What is the pathogenesis of Brucella?
- 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
What type of immunity is necessary to fight Brucella?
T cell immunity determines recovery
Ab are ineffective as it is intracellular
What are the major symptoms of brucellosis?
- Undulant Fever (kind of like in B. recurrentis)
- Splenomegaly, lymphadenopathy, hepatomegaly
What are the requirements for Brucella culture?
Requires enriched media and prolonged incubation to grow
What does Brucella look like under the microscope?
Grains of sand - they are very small in size
What is the treatment for Brucella infection?
Oral tetracyclines along with aminoglycosides for a prolonged time
What is the cause of tularemia?
Francisella tularensis
What is the transmission of F. tularensis?
Deer flies and ticks
Does F. tularensis have ovarian transfer in ticks?
Yes. there is transovarial transmission in ticks
What populations are at the greatest risk for tularemia?
- Hunters
- Lab workers
- People exposed to ticks
What states in the US have high tularemia incidence?
Missouri
Arkansas
Oklahoma
What are the reservoirs of tularemia?
Rabbits
Rodents
What Category is F. tularensis?
Category A
What is the pathogenesis of tularemia?
• 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
What kind of immunity is required to fight tularemia?
Cellular immunity
What are clinical manifestations of tularemia?
- Fever, chills, malaise 2-5 days after exposure
- Ulceroglandular infections
- Oculoglangular
- Typhoidal infection (ingestion of high number of organisms)
How is tularemia diagnosed?
- Immuno-fluorescent stain of smears for rapid diagnosis
- Acute and convalescent agglutinin antibody titers over time to assess Ab reaction
What are the requirements for F. tularensis culture?
- Requires sulfhydryl compounds for growth
- Requires extended incubation time
- Strict aerobe
What is the treatment for tularemia?
Streptomycin, gentamicin, tetracycline or choramphenicol
Removal of ticks promptly
What are characteristics of Pasteurella?
- Gram-negative, non-motile bacilli
- Facultative anaerobes
- Fermentative
What are carriers of Pasteurella?
- Normal respiratory and GI flora of cats and dogs
* Associated with cat & dog bites and scratches
What is the most common cause of pasteurellosis?
Cat bite
What is the most common Pasteurella species isolated from humans?
Pasteurella multocida
What are the growth requirements and characteristics of P. multocida?
• Grows on blood and chocolate but
not MacConkey agar
• Large buttery colonies with moth ball odor
What is unique about P. multocida in its response to penicillin?
It is sensitive to penicillin even though it is Gram negative
What is the cause of the plague?
Yersinia pestis
How is the plague transmitted?
Fleas
What is the Urban Plague?
Urban Plague-maintained in rat population and spread to humans by fleas
What is the Sylvatic Plague?
Sylvatic Plague-endemic in western USA. Carried by prairie dogs, mice, rabbits, rats.
What is the pathogenesis of the plague?
- 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
What is the plague called the Black Death?
Terminal cyanosis of the extremities
What states is the plague endemic to?
Arizona California Colorado New Mexico Oregon
What Category is Y. pestis?
Category A
What is the shape of the Y. pestis cells in culture?
Safety pins
What is used to treat the plague?
Streptomycin
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
E. Pasteurella
Which arthropod is the most important vector of tuleremia?
A. House fly B. Flea C. Lice D. Tsetse fly E. Tick
E. Tick
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
A. Brucella melitensis
