FASTIDIOUS GRAM NEGATIVE RODS. PART 8

Question 1

What disease is caused by francisella tularensis

Answer 1

Tularemia

Question 2

what differentiates the biotypes of francisella

Answer 2

distinguished on their virulence and epidemiology

Question 3

what are the biotypes of francisella tularensis

Answer 3

A and B

Question 4

Which animals are most commonly associated with Francisella tularensis?

Answer 4

Francisella tularensis has been isolated mostly from rabbits, deer, and a variety of rodents

Question 5

How is Francisella tularensis transmitted among animals?

Answer 5

It is transmitted among animals by vectors such as ticks, mites, and lice.

Question 6

What role do humans play in the transmission cycle?

Answer 6

Humans are accidental “dead-end” hosts, meaning they do not contribute significantly to the spread of the disease.

Question 7

What are the two rare routes of infection in humans?

Answer 7

1. Ingestion of infected meat: This can cause gastrointestinal tularemia.
2. Inhalation: This can lead to pneumonia.

Question 8

How does the organism enter the body in most cases?

Answer 8

The organism enters through the skin, forming an ulcer at the site

Question 9

Where does Francisella tularensis localize within the body?

Answer 9

It localizes to the cells of the reticuloendothelial system, where granulomas are formed.

Question 10

What other pathological features can occur during tularemia infection?

Answer 10

Caseation necrosis and abscesses can also occur.

Question 11

What primarily causes symptoms in tularemia?

Answer 11

Symptoms are primarily caused by endotoxin produced by the bacterium.

Question 12

What are the varying clinical presentations of tularemia?

Answer 12

1. Sudden onset of an influenza-like syndrome: Some cases present with symptoms similar to the flu.
2. Prolonged onset of a low-grade fever and adenopathy: In other cases, the fever is less severe, and there is swelling of lymph nodes (adenopathy).

Question 13

What is the most common type of tularemia?

Answer 13

Approximately 75% of cases are the “ulceroglandular” type. In this type, the site of entry (usually a skin ulcer) ulcerates, and the regional lymph nodes become swollen and painful.

Question 14

What are the less frequent forms of tularemia?

Answer 14

1. Glandular tularemia: Involves swollen lymph nodes.
2. Oculoglandular tularemia: Affects the eye and associated lymph nodes.
3. Typhoidal tularemia: Presents with a more systemic illness.
4. Gastrointestinal tularemia: Ingestion of infected meat leads to gastrointestinal symptoms.
5. Pulmonary tularemia: Inhalation of the bacterium causes pneumonia.

Question 15

What is the outcome regarding immunity after tularemia infection?

Answer 15

Tularemia usually confers lifelong immunity to the individual

Question 16

why is culturing of francisella species rarely undertaken

Answer 16

there is a high risk to laboratory workers of infection by inhalation

Question 17

Morphology of colonies on blood plate agar (BAP)

Answer 17

No growth

Question 18

Morphology of colonies on macConkey agar (MAC)

Chocolate agar is an enriched medium that provides essential nutrients for fastidious organisms.

Answer 18

No growth

Question 19

Morphology of colonies on chocolate agar

Answer 19

Small, smooth, gray gram negative coccobacilli at 2 -5 days

Question 20

what is special media required

Answer 20

Requires special media (BCYE or MTM)

Question 21

biochemical results of francisella tularensis

Answer 21

1. Oxidase: negative
2. Catalase: negative- weak positive
3. Ferments glucose
4. X and V negative

Question 21

Treatment and prevention of francisella tularensis

Answer 21

1. Streptomycin
2. Avoiding both being bitten by ticks and handling wild animals.
3. Vaccine to those whose occupation brings them into close contact with wild
   animals(not available commercially).