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MHD 1 > L30 Bacterial Zoonoses > Flashcards

L30 Bacterial Zoonoses Flashcards

1
Q

What is a disease transmitted from animals to humans?

A

Zoonosis

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2
Q

Brucellosis is found worldwide; what does it cause in animals?

A

Spontaneous abortions in sheep, cattle, pigs, and dogs

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3
Q

How are humans infected with brucellosis?

A

Contact with animals or ingestion of contaminated milk or dairy products (particularly unpasteurized dairy products); it can also be inhaled.

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4
Q

What are the four species of Brucella and in what animals are they found?

A

B. melitensis (goats, sheep, camels)
B. suis (pigs)
B. abortus (cattle)
B. canis (dogs)

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5
Q

Which species of Brucella is most responsible for human infections?

A

B. melitensis

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6
Q

Brucellosis is a category ___ biothreat agent. Why is it a biothreat agent?

A

B; it can be aerosolized

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7
Q

What are the three primary routes of infection for Brucellosis?

A

Ingestion, inhalation, inoculation

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8
Q

Describe the pathogenesis of Brucella.

A

Organisms penetrate the skin or mucous membranes. They are phagocytosed by macrophages and monocytes and carried to the spleen, liver, bone marrow, lymph nodes, and kidneys. Organisms multiply in macrophages in the RES. The host ultimately forms small granulomas.

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9
Q

What are the host defense implications of Brucella being an intracellular organism?

A

Humoral immunity is irrelevant (thus, T cell immunity determines recovery)

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10
Q

Why does Brucella survive intracellularly?

A

They can inhibit PMN leukocyte degranulation.

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11
Q

Brucella has a predilection for ___ tissues in animals.

A

Erythritol-rich

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12
Q

Symptoms of Brucella appear ___ weeks after exposure.

A

2-8

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13
Q

Describe the clinical manifestations of Brucella.

A

Initially: non-specific symptoms (malaise, chills, sweats, fatigue, weakness, myalgias)

Undulating fever/fever of unknown origin

Splenomegaly, lymphadenopathy, hepatomegaly

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14
Q

What are the advanced diseases caused by Brucella?

A 
GI symptoms
Osteolytic lesions or joint effusion
Respiratory symptoms
Meningitis/meningoencephalitis
Endocarditis with septic embolization
Orchitis
Renal granulomas
Endophthalmitis from hematogenous dissemination
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15
Q

Chronic infection with Brucella leads to symptom development in ___ months.

A

3-6

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16
Q

How is brucella diagnosed?

A
  1. Blood cultures (extended incubation)
  2. Bone marrow or infected tissue cultures
  3. Serology
  4. Elevated febrile agglutinin titer
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17
Q

What are the features of Brucella?

A
  1. Small coccobacillus Gram negative rod - porr staining, looks like fine sand
  2. Slow growing, requires enriched media
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18
Q

How is Brucellosis treated?

A

With agents that penetrate phagocytic cells - oral tetracycines, aminoglycosides

Surgical intervention may be necessary in some cases

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19
Q

Describe the effect of cephalosporins and fluroquinolones on Brucellosis.

A

Poor activity, patients may relapse (10% of the time)

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20
Q

How can Brucellosis be prevented?

A

Immunize livestock, avoid unpasteurized milk and dairy products

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21
Q

True or false - there is no human vaccine for Brucellosis.

A

True

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22
Q

What causes tularemia?

A

Francisella tularensis

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23
Q

How is tularemia transmitted?

A

Wild animals, transovarial transmission in ticks, deer flies, domestic pets that catch infected animals, consumption of contaminated meat or water

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24
Q

Most tularemia patients are men - why?

A

They are hunters.

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25
Q

Tularemia is a potential ___ agent.

A

Biothreat

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26
Q

Describe the pathogenesis of tularemia.

A

The organism enters through breaks in the skin or mucous membranes. Low inoculation needed. An ulcer may develop at the entry site. Organisms disseminate via the blood stream, and the host responds by forming a granuloma.

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27
Q

Why is cellular immunity required for recovery from tularemia?

A

It is a facultative intracellular organism and humoral immunity is less effective.

28
Q

Describe the clinical manifestations of tularemia.

A
  1. Fever, chills, malaise 2-5 days after exposure;
  2. Ulceroglandular infections (most common form) - papule forms at the site, becomes necrotic and ulcerates; the regional lymph nodes swell
  3. Oculoglandular inefctions (conjunctival inoculation, unilateral painful conjunctivitis)
  4. Typhoidal infection (fever, prostration, weight loss, highest portality)
  5. Pneumonic infection
  6. Glandular form (adenopathy)
  7. Oropharyngeal form (ingestion of infected meat or water, fever/throat pain with exudative pharyngitis or tonsillitis, pharyngeal ulcers and pseudomembranes, cervical, pre-parotid, and retropharyngeal lymphadenopathy)
29
Q

Rabbit associated cases of tularemia involve ulceroglandular infection of the ___ and ___.

A

Fingers; hands

30
Q

Tick associated cases of tularemia involve ulceroglandular infection what body parts?

A

Trunk, perineum, legs, head, neck

31
Q

How is tularemia diagnosed?

A

Immunofluorescent stain
Culture requires special conditions
Serologic: acute and convalescent agglutinin and Ab titers

32
Q

What are the features of F. tularensis?

A
  1. Culture from blood, pleural fluids, lymph nodes, wound, conjunctival swabs, tissue, respiratory tract secretions
  2. Very small gram negative coccobacilli
  3. Requires sulfhydryl compounds and extended time to grow, grows on chocolate agar in 2-3 weeks
  4. Obligate aerobe
  5. Non-motile
33
Q

How is tularemia treated?

A

Streptomycin, genatmicin, tetracycline, choramphenicol; remove ticks

34
Q

How is tularemia prevented?

A

Avoid contact with dead animals

35
Q

What are the features of Pasteurella spp?

A
  1. Gram-negative bacilli
  2. Non-motile
  3. Facultative anaerobes
  4. Fermentative
  5. Associated with animals
36
Q

How is pasteurella acquired?

A

From cat and dog bites/scratches (normal respiratory/GI flora for cats and dogs); respiratory route

37
Q

Which type of pasteurella is more common: multocida or canis?

A

Multocida (cat)

38
Q

Most human infections with pastreuella are wound infections/cellulitis following ___ bites.

A

Cat

39
Q

Describe infection with pasteurella.

A

Wound infections/cellulitis with pain, swelling, and serosanguinous drainage at the wound site. Septic arthritis and osteomyelitis may occur following a deep puncture wound.

40
Q

What is the most common species of Pasteurella isolated from humans?

A

P. multocida

41
Q

Describe the features of P. multocida.

A
  1. Small, bipolar Gram negative rods
  2. Facultative anaerobe
  3. Grows on blood, chocolate, NOT MacConkey
  4. Indole positive (large buttery colonies, moth ball odor)
  5. Oxidase positive
  6. Catalase positive
  7. Penicillin susceptible
42
Q

How is pasteurella diagnosed?

A

Culture lesion site and blood

43
Q

How is pasteurella treated?

A

Penicillin

44
Q

How is the plague transmitted?

A

Flea bite, direct contact with infected tissues, inhalation of infected aerosols/from patient with pulmonary disease

45
Q

What causes the plague?

A

Y. pestis

46
Q

What are the two forms of the plague and how are they spread?

A
  1. Urban: maintained in rats, spread to humans by fleas

2. Sylvatic: endemic in western USA, carried by praire dogs, mice, rabbits, rats

47
Q

Describe the pathogenesis of the plague.

A

Organisms multiply in the flea’s gut. The flea bites humans or other rodents. The organisms move from the bite site to the lymph nodes, where they multiply and cause necrosis and swelling = bubo. They move to the blood, lungs, liver, and spleen

48
Q

True or false - Y. pestis are obligate intracellular organisms.

A

False - they are facultative and can multiply freely in the extracellular environment and also resist killing within phagocytes

49
Q

What are the major symptoms of the plague?

A
  1. Enlarge dtender lymph nodes with hemorrhagic necrosis and black buboes
  2. Systemic infection in the liver, lungs, and spleen
  3. Pneumonic disease with necrotizing hemorrhagic pneumonia
  4. Terminal cyanosis = black death
50
Q

What are the clinical syndromes associated with Y. pestis?

A
  1. Bubonic plague
  2. Septicemia plague
  3. Pneumonic plague
51
Q

What are the symptoms of bubonic plague?

A

Fever and painful bubo 2-7 days after a bite; patients present with sudden onset of fever, chills, weakness, and headache. Within hours, they notice intense pain in the bubo-filled region and become prostrate and lethargic.

52
Q

___% with bubonic plague have ___ (+/-) blood cultures.

A

Positive

53
Q

What is the mortality rate if bubonic plague is untreated?

A

75%

54
Q

What are the symptoms of the septicemic plague?

A

High fever, delirium seizures in children, septic shock, DIC, black hemorrhagic splotches

55
Q

True or false - 100% of patients become septic with blood cultures.

A

True

56
Q

Why is that fatality rate of septicemic plague high?

A

Delayed diagnosis and treatment

57
Q

What are the symptoms of the pnemonic plague?

A

Initially, headache, malaise, fever, vomiting, prostration, confusion; patients develop cough, chest pain, and hemoptysis. Sputum is usually purulent and contains Y. pestis. Sepsis and death quickly follow.

58
Q

When should the plague be on the differential?

A

In febrile patients who have been exposed to rodents or other mammals in known epidemic areas of the world

59
Q

What is on the differential in addition to the plague?

A

Reye’s syndrome, tularemia, bacterial pneumonia, acute surgical abdomen

60
Q

Yersinia pestis is a category ___ bioterrorism agent.

A

A

61
Q

How can the plague be diagnosed?

A

Smear and culture of bubo aspirate, blood, or sputum sample

62
Q

What are important lab findings in the plague?

A

WBC count of 10,000 to 20,000 cells/mm3; platelet count normal or low with DIC

63
Q

What are the key features of Y. pestis?

A
  1. Oxidase negative
  2. Non-motile
  3. Small/cocco-bacillary, bipolar staining, safety pins
  4. Fried egg on ordinary media
  5. Small pinpoint colonies on MacConkey
  6. Grow faster at 28 C than 37 C
64
Q

How is Y. pestis treated?

A

Streptomycin

Alternatives: gentamicin, chloramphenicol, tetracyclines

65
Q

Which antibiotics are not effective in treating the plague?

A

Penicillin, cephalosporin

66
Q

What are preventative measures to avoid the plague?

A

Avoid contact with dead rodents, chemoprophylaxis with tetracycline, rat and flea control measures, vaccine for high risk patients

MHD 1 (58 decks)

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