36 Francisella and Brucella

Question 1

Describe the structural morphology of Francisella?

Answer 1

• Very small, faintly-staining G(-) coccobacillus, nonmotile, thin lipid capsule and most strains require cystine for growth, strictly aerobic.

Question 2

What is the species of Francisella that causes tularemia?

Answer 2

• F. tularensis aka glandular fever, rabbit fever, tick fever and deer fly fever.

Question 3

What are the two subdivision of F. tularensis?

Answer 3

• Tularensis (type A) and holarctica (type B)

Question 4

What vector is associated with type A and what for type B?

Answer 4

• Type A: lagomorphs (rabbits, hares) and cats

- Type B: Rodents and cats

Question 5

How is tularemia diagnosed in most patients?

Answer 5

• Finiding of a fourfold or greater increase in titer of antibodies during the illness or a single titer of 1:160 or greater.

Question 6

What is the treatment for Tuleramia?

Answer 6

• Gentamicin

Question 7

Which species 4 species of Brucella are associated with human disease?

Answer 7

• B. abortus, B. melitensis, B. suis, B. canis

Question 8

Describe the structural morphology of Brucellae.

Answer 8

• Small, nonmotile, nonencapsulated, G(-) coccobacilli. Strictly aerobic and does not ferment carbohydrates.

Question 9

How can brucellae survive and replicate inside the host?

Answer 9

• They are intracellular parasites: they replicate inside phagocytic cells by inhibiting phagolysosome fusion, preventing release of toxic enzymes from intracellular granules, suppressing production of TNF-alpha and inactivating hydrogen peroxide and superoxide by procution of catalase andsuperoxide dismutase.

Question 10

What are the different reservoirs for each strain of Brucellae?

Answer 10

• B. melitensis: goats and sheeps
• B. abortus: cattle, American bison
• B. suis: swine, reindeer, caribou
• B. canis: dogs, foxes and coyotes

Question 11

Brucellae has a propensity for infecting organs rich in what? And where is it found?

Answer 11

• Erythritol (not in humans) found in breast, uterus, placenta, and epididymis.

Question 12

What is the disease spectrum for each strain of Brucellae?

Answer 12

• B. canis and abortus tend to produce mild disease with rare suppurative complications
• B suis causes the formation of destructive lesions and has a prolonged course.
• B, melitensis causese severe disease w/ high incidence of serious complication.
  What are the clinical manifestations of acute brucellosis?
• Symptoms appear 1-3 weeks after exposure. Initial are nonspecific and consists of malaise, chills, sweats, fatigue, weakness, myalgias, weight loss, arthralgias and nonproductive cough. Almost all patients have fever and can be intermittent in untreated patients, hence the name undulant fever.

Question 13

What is relapse of the disease associated with?

Answer 13

• Persistan focus on infection (e.g., in bone, spleen, liver) and not with the development of antibiotic resistance.

Question 14

How is brucellosis identified?

Answer 14

• Microscopic and colonial morphology, positive oxidase and urase reactions and reactivity with antibodies directed at all Brucellae strains exept canis.

Question 15

What is the treatment for brucellosis?

Answer 15

• Doxycycline with rifampin for 6 weeks or longer.

Question 16

What are the clinical manifestations of disease caused by F. tularesis? Which one is the most common?

Answer 16

• Symptoms and prognosis determined by route of infection: ulceroglandular, oculoglandurlar, glandular typhoidal, oropharyngeal, gastrointestinal, pneumonic. Ulceroglandular is the most common.