Exotic and Biohazard Pneumonias II

Question 1

Descirbe Francisella tularensis

Answer 1

a gram-negative rod that has a pleomorphic appearance upon staining. It is also an intracellular pathogen that is well adapted for survival within macrophages

Question 2

What are the biotypes of Francisella?

Answer 2

A- more severe and found mostly in the US

B- less severe in Europe

Question 3

Virulence factors of Fancisella?

Answer 3

Ft produces an LPS that cannot be recognized by TLR-4 and may produce a capsule

Question 4

How is Ft transmitted?

Answer 4

Ft can be transmitted via mites, lice, and ticks, with ticks being the most common
vector. These vectors acquire the bacterium from infected animals in the wild, and it should be noted that Ft is endemic in animals and has been isolated from >100 different animal species.

Acquired via contact of contaminated blood or water with skin abrasions.

Ingestion of contaminated food or water.

Inhalation of aerosolized Ft (results in the most severe form of disease)

Question 5

What is the reservoir of Ft?

Answer 5

The actual reservoir of Ft has not been determined. It can survive in animals, in insects, in water, and in amoebas (maybe how it survives in water).

Question 6

Where are most Ft cases clustered in the U.S.?

Answer 6

Arkansas and Missouri and Martha’s vineyard, MA

Question 7

How are the majority of infections in the Midsouth transmitted?

Answer 7

Of the ulceroglandular type

and are typically contracted through contact with blood from infected animals via skin abrasions (e.g. hunters)

Question 8

What is the LD50 of Ft?

Answer 8

less than 10 when inhaled (extremely pathogenic)

Question 9

What is the most common form of Ft?

Answer 9

The ulceroglandular form (75%) that occurs when the infection is acquired through a skin lesion.

This form of disease is characterized by the presence of a skin lesion or ulcer at the infection site that is accompanied by pronounced bubo-like LAD of local nodes. This form of disease carries a 1-3% mortality rate BUT can disseminate to the lungs resulting in a much more serious disease.

Question 10

Other forms of Ft?

Answer 10

• GI (via food)
• Oculoglandular
• Pneumonic
• Typhoidal

Question 11

How does Ft present?

Answer 11

rapid-onset flu-like symptoms.

Many patients also present with prolonged low-grade fever and LAD. Most cases (75%) are of the ulceroglandular type and include a lesion at the inoculation site as well as bubo-like swollen regional
lymph nodes.

Question 12

T or F. Patients are typically left with lifelong immunity to Ft if they survive the initial tularemic disease.

Answer 12

T.

Question 13

How is diagnosis of Ft made?

Answer 13

agglutination testing that involves both acute-phase (if a sample was collected) and convalescent phase serum.

Fluorescent antibody staining of infected tissue can also be
performed.

Culture of Ft from patients is very rare due to both the lack of available media that will support growth of the bacterium and the inherent dangers to medical personnel.

Question 14

Vaccine for Ft

Answer 14

An unlicensed vaccine, known as the live vaccine strain (an attenuated type B strain of Ft), is available to military personnel (but not to the general public) and an individual that has received the vaccine would test positive in agglutination testing, even in the absence of Ft infection. Luckily, only military personnel
and a select few other people have received this vaccine.

Question 15

How is FT treated?

Answer 15

Streptomycin. No significant

development of antibiotic resistance has been noted for Ft

Question 16

Hantavirus belongs to what family?

Answer 16

Bunyaviridae

Question 17

Describe the structure of Hantavirus

Answer 17

enveloped, trisegmented, single stranded, negative sense RNA virus found mostly in the Middle East and Asia

Question 18

How is hantavirus transmitted? Treatment?

Answer 18

aerosolized rodent excreta

Treatment: Ribavirin

Question 19

What type of Hantavirus causes Hantavirus pulmonary syndrome?

Answer 19

Sin Nombre virus

Question 20

How does HPS present?

Answer 20

mostly in healthy young adults and shows prodrome of ever and muscle aches, rapidly progressing to pulmonary edema and respiratory failure. Death usually occurs within 2-5 days

Question 21

What is the primary carrier of Sin Nombre?

Answer 21

deer mouse (and some white-footed mice, cotton rats, and rice rats)

Note that guinea pigs, hamsters, and gerbils are not known to carry it

Question 22

What is the incubation period of HPS before symptoms?

Answer 22

14-17 days

Question 23

Initial signs of HPS?

Answer 23

fatigue, fever, myalgia of the large muscle groups (thighs, hips, back, shoulders), and headache lasting 3
to 5 days.

Question 24

Later signs of HPS?

Answer 24

• coughing and SOB

- pulmonary edema and hypotension

Question 25

How is HPS treated?

Answer 25

Requires early and aggressive

intensive care, focusing on electrolyte balance, oxygenation of the blood, and maintaining blood pressure.

Question 26

Describe Yersinia pestis (plague)

Answer 26

gram-negative encapsulated rod that is well-adapted for survival and growth in
macrophages, and is classified as an intracellular bacterial pathogen.

Question 27

What is the LD50 of Yp?

Answer 27

between 1 and 10 CFU when it enters via the respiratory route.

Question 28

How does Yp look upon staining?

Answer 28

Bipolar staining pattern that makes it resemble a safety pin with a clear area in the center.

Question 29

What is the main reservoir for Yp?

Answer 29

rats (In the U.S., prairie dogs). Almost all cases occur in Southeast Asia.

Question 30

How is Yp transmitted from rats to humans?

Answer 30

via fleas. However, person-to-person transmission is possible via inhalation of aerosolized droplets containing Yp.

Aerosol transmission results in the most serious and always fatal (without early
antibiotic treatment) pneumonic form of plague.

Question 31

What happens when Yp is introduced by fleas?

Answer 31

it spreads to the regional lymph nodes. Soon after this dissemination occurs, the lymph node becomes painful and very swollen.

Question 32

What is the name of the initial affected nodes?

Answer 32

Buboes, and their appearance lead to the designation for the most common form of plague, the bubonic plague.

The infection typically becomes bacteremic, reaching high conc. in the bloodstream and
then disseminating to many organs.

Question 33

Virulence determinants of Yp?

Answer 33

1) The polysaccharide-protein capsule protects against phagocytosis, allowing for dissemination via the bloodstream.
2) The LPS is an endotoxin that interferes with normal cytokine production by the various immune cell types that respond to the infection. This prevents the immune system from responding in an efficient manner to the infection.
3) Two proteins (the V and W antigens) that allow intra-macrophage survival and growth
4) A series of Yersinia outer proteins (Yops), that are injected by a type III secretion system into host cells, that inhibit phagocytosis and host cytokine production by phagocytes.
5) exotoxin

Question 34

What are the forms of plague?

Answer 34

1) bubonic plague that typically results from vector-transmitted infection. This
forms begins with bubo formation.

2) The pneumonic plague, and always results when the bacterium is transmitted via the aerosol route, and it can sometimes result from dissemination of Yp to the lungs during bubonic plague.

The bubonic form of disease is 50% fatal, while the pneumonic form of disease is
essentially 100% fatal without early antibiotic intervention.

Question 35

How does Yp present?

Answer 35

high fever, myalgias, and collapse due to extreme fatigue (prostration). Septic shock can occur and along with pneumonic disease is the primary life-threatening consequence of plague.

Question 36

What are the symptoms of pneumonic plague?

Answer 36

• fever, headache
• cough, hemoptysis, dyspnea, chest pain
• muscle weakness

Question 37

How is Yp diagnosed?

Answer 37

Geimsa or Wayson stains can reveal the typical “safety-pin” appearance of Yp, and both are superior to gram staining for this purpose.

Fluorescent antibody staining, using antibodies specific for Yp determinants can be performed using tissues collected from the patient.

Question 38

Treatment of plague

Answer 38

ideally involves both streptomycin and tetracycline, but streptomycin can be used alone if necessary.

Because plague progresses very quickly, suspected cases should be treated ASAP instead of waiting for the results of staining and antibody titering.

Question 39

Vaccine for Yp

Answer 39

A partially effective vaccine that consists of a formalin-killed whole Yp formulation.

Question 40

Which forms of Yp is the vaccine effective against?

Answer 40

Bubonic but not pneumonic plague.